Spring Security配置

論壇上看了不少Spring Security的相關文章。這些文章基本上都還是基於Acegi-1.X的配置方式，而主要的配置示例也來自於SpringSide的貢獻。

衆所周知，Spring Security針對Acegi的一個重大的改進就在於其配置方式大大簡化了。所以如果配置還是基於Acegi-1.X這樣比較繁瑣的配置方式的話，那麼我們還不如直接使用Acegi而不要去升級了。所以在這裏，我將結合一個示例，重點討論一下Spring Security 2是如何進行配置簡化的。

搭建基礎環境

首先我們爲示例搭建基本的開發環境，環境的搭建方式，可以參考我的另外一篇文章：http://www.iteye.com/wiki/struts2/1321-struts2-development-environment-to-build

整個環境的搭建包括：創建合適的目錄結構、加入了合適的Library，加入了基本的Jetty啓動類、加入基本的配置文件等。最終的項目結構，可以參考我的附件。

參考文檔

這裏主要的參考文檔是Spring Security的自帶的Reference。網絡上有一個它的中文翻譯，地址如下：http://www.family168.com/tutorial/springsecurity/html/springsecurity.html

除此之外，springside有一個比較完整的例子，不過是基於Acegi的，我也參閱了其中的一些實現。

Spring Security基本配置

Spring Security是基於Spring的的權限認證框架，對於Spring和Acegi已經比較熟悉的同學對於之前的配置方式應該已經非常瞭解。接下來的例子，將向大家展示Spring Security基於schema的配置方式。

最小化配置

1. 在web.xml文件中加入Filter聲明

<!-- Spring security Filter -->
<filter>
    <filter-name>springSecurityFilterChain</filter-name>
    <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>
<filter-mapping>
    <filter-name>springSecurityFilterChain</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

<!-- Spring security Filter -->
<filter>
    <filter-name>springSecurityFilterChain</filter-name>
    <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>
<filter-mapping>
    <filter-name>springSecurityFilterChain</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

這個Filter會攔截所有的URL請求，並且對這些URL請求進行Spring Security的驗證。

注意，springSecurityFilterChain這個名稱是由命名空間默認創建的用於處理web安全的一個內部的bean的id。所以你在你的Spring配置文件中，不應該再使用這個id作爲你的bean。

與Acegi的配置不同，Acegi需要自行聲明一個Spring的bean來作爲Filter的實現，而使用Spring Security後，無需再額外定義bean，而是使用<http>元素進行配置。

2. 使用最小的<http>配置

<http auto-config='true'>
    <intercept-url pattern="/**" access="ROLE_USER" />
</http>

<http auto-config='true'>
    <intercept-url pattern="/**" access="ROLE_USER" />
</http>

這段配置表示：我們要保護應用程序中的所有URL，只有擁有ROLE_USER角色的用戶才能訪問。你可以使用多個<intercept-url>元素爲不同URL的集合定義不同的訪問需求，它們會被歸入一個有序隊列中，每次取出最先匹配的一個元素使用。 所以你必須把期望使用的匹配條件放到最上邊。

3. 配置UserDetailsService來指定用戶和權限

接下來，我們來配置一個UserDetailsService來指定用戶和權限：

<authentication-provider>
    <user-service>
      <user name="downpour" password="downpour" authorities="ROLE_USER, ROLE_ADMIN" />
      <user name="robbin" password="robbin" authorities="ROLE_USER" />
      <user name="QuakeWang" password="QuakeWang" authorities="ROLE_ADMIN" />
    </user-service>
  </authentication-provider>

<authentication-provider>
    <user-service>
      <user name="downpour" password="downpour" authorities="ROLE_USER, ROLE_ADMIN" />
      <user name="robbin" password="robbin" authorities="ROLE_USER" />
      <user name="QuakeWang" password="QuakeWang" authorities="ROLE_ADMIN" />
    </user-service>
  </authentication-provider>

在這裏，downpour擁有ROLE_USER和ROLE_ADMIN的權限，robbin擁有ROLE_USER權限，QuakeWang擁有ROLE_ADMIN的權限

4. 小結

有了以上的配置，你已經可以跑簡單的Spring Security的應用了。只不過在這裏，我們還缺乏很多基本的元素，所以我們尚不能對上面的代碼進行完整性測試。

如果你具備Acegi的知識，你會發現，有很多Acegi中的元素，在Spring Security中都沒有了，這些元素包括：表單和基本登錄選項、密碼編碼器、Remember-Me認證等等。

接下來，我們就來詳細剖析一下Spring Security中的這些基本元素。

剖析基本配置元素

1. 有關auto-config屬性

在上面用到的auto-config屬性，其實是下面這些配置的縮寫：

<http>
    <intercept-url pattern="/**" access="ROLE_USER" />
    <form-login />
    <anonymous />
    <http-basic />
    <logout />
    <remember-me />
</http>

<http>
    <intercept-url pattern="/**" access="ROLE_USER" />
    <form-login />
    <anonymous />
    <http-basic />
    <logout />
    <remember-me />
</http>

這些元素分別與登錄認證，匿名認證，基本認證，註銷處理和remember-me對應。 他們擁有各自的屬性，可以改變他們的具體行爲。

這樣，我們在Acegi中所熟悉的元素又浮現在我們的面前。只是在這裏，我們使用的是命名空間而已。

2. 與Acegi的比較

我們仔細觀察一下沒有auto-config的那段XML配置，是不是熟悉多了？讓我們來將基於命名空間的配置與傳統的Acegi的bean的配置做一個比較，我們會發現以下的區別：

1) 基於命名空間的配置更加簡潔，可維護性更強

例如，基於命名空間進行登錄認證的配置代碼，可能像這樣：

<form-login login-page="/login.jsp" authentication-failure-url="/login.jsp?error=true" default-target-url="/work" />

<form-login login-page="/login.jsp" authentication-failure-url="/login.jsp?error=true" default-target-url="/work" />

如果使用老的Acegi的Bean的定義方式，可能像這樣：

<bean id="authenticationProcessingFilter"
          class="org.acegisecurity.ui.webapp.AuthenticationProcessingFilter">
    <property name="authenticationManager"
                  ref="authenticationManager"/>
    <property name="authenticationFailureUrl"
                  value="/login.jsp?error=1"/>
    <property name="defaultTargetUrl" value="/work"/>
    <property name="filterProcessesUrl"
                  value="/j_acegi_security_check"/>
    <property name="rememberMeServices" ref="rememberMeServices"/>
</bean>

<bean id="authenticationProcessingFilter"
		  class="org.acegisecurity.ui.webapp.AuthenticationProcessingFilter">
	<property name="authenticationManager"
				  ref="authenticationManager"/>
	<property name="authenticationFailureUrl"
				  value="/login.jsp?error=1"/>
	<property name="defaultTargetUrl" value="/work"/>
	<property name="filterProcessesUrl"
				  value="/j_acegi_security_check"/>
	<property name="rememberMeServices" ref="rememberMeServices"/>
</bean>

這樣的例子很多，有興趣的讀者可以一一進行比較。

2) 基於命名空間的配置，我們無需再擔心由於過濾器鏈的順序而導致的錯誤

以前，Acegi在缺乏默認內置配置的情況下，你需要自己來定義所有的bean，並指定這些bean在過濾器鏈中的順序。一旦順序錯了，很容易發生錯誤。而現在，過濾器鏈的順序被默認指定，你不需要在擔心由於順序的錯誤而導致的錯誤。

3. 過濾器鏈在哪裏

到目前爲止，我們都還沒有討論過整個Spring Security的核心部分：過濾器鏈。在原本Acegi的配置中，我們大概是這樣配置我們的過濾器鏈的：

<bean id="filterChainProxy"
          class="org.acegisecurity.util.FilterChainProxy">
    <property name="filterInvocationDefinitionSource">
        <value>
                CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON
                PATTERN_TYPE_APACHE_ANT
                /common/**=#NONE#
                /css/**=#NONE#
                /images/**=#NONE#
                /js/**=#NONE#
                /login.jsp=#NONE#
                /**=httpSessionContextIntegrationFilter,logoutFilter,authenticationProcessingFilter,securityContextHolderAwareRequestFilter,exceptionTranslationFilter,filterSecurityInterceptor
        </value>
    </property>
</bean>

<bean id="filterChainProxy"
		  class="org.acegisecurity.util.FilterChainProxy">
	<property name="filterInvocationDefinitionSource">
		<value>
				CONVERT_URL_TO_LOWERCASE_BEFORE_COMPARISON
				PATTERN_TYPE_APACHE_ANT 				
				/common/**=#NONE# 
				/css/**=#NONE# 
				/images/**=#NONE#
				/js/**=#NONE# 
				/login.jsp=#NONE#
				/**=httpSessionContextIntegrationFilter,logoutFilter,authenticationProcessingFilter,securityContextHolderAwareRequestFilter,exceptionTranslationFilter,filterSecurityInterceptor
		</value>
	</property>
</bean>

其中，每個過濾器鏈都將對應於Spring配置文件中的bean的id。

現在，在Spring Security中，我們將看不到這些配置，這些配置都被內置在<http>節點中。讓我們來看看這些默認的，已經被內置的過濾器：


這些過濾器已經被Spring容器默認內置註冊，這也就是我們不再需要在配置文件中定義那麼多bean的原因。

同時，過濾器順序在使用命名空間的時候是被嚴格執行的。它們在初始化的時候就預先被排好序。不僅如此，Spring Security規定，你不能替換那些<http>元素自己使用而創建出的過濾器，比如HttpSessionContextIntegrationFilter, ExceptionTranslationFilter 或 FilterSecurityInterceptor。

當然，這樣的規定是否合理，有待進一步討論。因爲實際上在很多時候，我們希望覆蓋過濾器鏈中的某個過濾器的默認行爲。而Spring Security的這種規定在一定程度上限制了我們的行爲。

不過Spring Security允許你把你自己的過濾器添加到隊列中，使用custom-filter元素，並且指定你的過濾器應該出現的位置：

<beans:bean id="myFilter" class="com.mycompany.MySpecialAuthenticationFilter">
    <custom-filter position="AUTHENTICATION_PROCESSING_FILTER"/>
</beans:bean>

<beans:bean id="myFilter" class="com.mycompany.MySpecialAuthenticationFilter">
    <custom-filter position="AUTHENTICATION_PROCESSING_FILTER"/>
</beans:bean>

不僅如此，你還可以使用after或before屬性，如果你想把你的過濾器添加到隊列中另一個過濾器的前面或後面。 可以分別在position屬性使用"FIRST"或"LAST"來指定你想讓你的過濾器出現在隊列元素的前面或後面。

這個特性或許能夠在一定程度上彌補Spring Security的死板規定，而在之後的應用中，我也會把它作爲切入點，對資源進行管理。

另外，我需要補充一點的是，對於在http/intercept-url中沒有進行定義的URL，將會默認使用系統內置的過濾器鏈進行權限認證。所以，你並不需要在http/intercept-url中額外定義一個類似/**的匹配規則。

使用數據庫對用戶和權限進行管理

一般來說，我們都有使用數據庫對用戶和權限進行管理的需求，而不會把用戶寫死在配置文件裏。所以，我們接下來就重點討論使用數據庫對用戶和權限進行管理的方法。

用戶和權限的關係設計

在此之前，我們首先需要討論一下用戶（User）和權限（Role）之間的關係。Spring Security在默認情況下，把這兩者當作一對多的關係進行處理。所以，在Spring Security中對這兩個對象所採用的表結構關係大概像這樣：

CREATE TABLE users (
  username VARCHAR(50) NOT NULL PRIMARY KEY,
  password VARCHAR(50) NOT NULL,
  enabled BIT NOT NULL
);

CREATE TABLE authorities (
  username VARCHAR(50) NOT NULL,
  authority VARCHAR(50) NOT NULL
);

CREATE TABLE users (
  username VARCHAR(50) NOT NULL PRIMARY KEY,
  password VARCHAR(50) NOT NULL,
  enabled BIT NOT NULL
);

CREATE TABLE authorities (
  username VARCHAR(50) NOT NULL,
  authority VARCHAR(50) NOT NULL
);

不過這種設計方式在實際生產環境中基本上不會採用。一般來說，我們會使用邏輯主鍵ID來標示每個User和每個Authorities（Role）。而且從典型意義上講，他們之間是一個多對多的關係，我們會採用3張表來表示，下面是我在MySQL中建立的3張表的schema示例：

CREATE TABLE `user` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) default NULL,
  `password` varchar(255) default NULL,
  `disabled` int(1) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `role` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `user_role` (
  `user_id` int(11) NOT NULL,
  `role_id` int(11) NOT NULL,
  PRIMARY KEY  (`user_id`,`role_id`),
  UNIQUE KEY `role_id` (`role_id`),
  KEY `FK143BF46AF6AD4381` (`user_id`),
  KEY `FK143BF46A51827FA1` (`role_id`),
  CONSTRAINT `FK143BF46A51827FA1` FOREIGN KEY (`role_id`) REFERENCES `role` (`id`),
  CONSTRAINT `FK143BF46AF6AD4381` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `user` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) default NULL,
  `password` varchar(255) default NULL,
  `disabled` int(1) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `role` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `user_role` (
  `user_id` int(11) NOT NULL,
  `role_id` int(11) NOT NULL,
  PRIMARY KEY  (`user_id`,`role_id`),
  UNIQUE KEY `role_id` (`role_id`),
  KEY `FK143BF46AF6AD4381` (`user_id`),
  KEY `FK143BF46A51827FA1` (`role_id`),
  CONSTRAINT `FK143BF46A51827FA1` FOREIGN KEY (`role_id`) REFERENCES `role` (`id`),
  CONSTRAINT `FK143BF46AF6AD4381` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

通過配置SQL來模擬用戶和權限

有了數據庫的表設計，我們就可以在Spring Security中，通過配置SQL，來模擬用戶和權限，這依然通過<authentication-provider>來完成：

<authentication-provider>
    <jdbc-user-service data-source-ref="dataSource"
    users-by-username-query="SELECT U.username, U.password, U.accountEnabled AS 'enabled' FROM User U where U.username=?"
    authorities-by-username-query="SELECT U.username, R.name as 'authority' FROM User U JOIN Authority A ON u.id = A.userId JOIN Role R ON R.id = A.roleId WHERE U.username=?"/>
</authentication-provider>

<authentication-provider>
    <jdbc-user-service data-source-ref="dataSource"
    users-by-username-query="SELECT U.username, U.password, U.accountEnabled AS 'enabled' FROM User U where U.username=?"
    authorities-by-username-query="SELECT U.username, R.name as 'authority' FROM User U JOIN Authority A ON u.id = A.userId JOIN Role R ON R.id = A.roleId WHERE U.username=?"/>
</authentication-provider>

這裏給出的是一個使用SQL進行模擬用戶和權限的示例。其中你需要爲運行SQL準備相應的dataSource。這個dataSource應該對應於Spring中的某個bean的定義。

從這段配置模擬用戶和權限的情況來看，實際上Spring Security對於用戶，需要username，password，accountEnabled三個字段。對於權限，它需要的是username和authority2個字段。

也就是說，如果我們能夠通過其他的方式，模擬上面的這些對象，並插入到Spring Security中去，我們同樣能夠實現用戶和權限的認證。接下來，我們就來看看我們如何通過自己的實現，來完成這件事情。

通過擴展Spring Security的默認實現來進行用戶和權限的管理

事實上，Spring Security提供了2個認證的接口，分別用於模擬用戶和權限，以及讀取用戶和權限的操作方法。這兩個接口分別是：UserDetails和UserDetailsService。

public interface UserDetails extends Serializable {

    GrantedAuthority[] getAuthorities();

    String getPassword();

    String getUsername();

    boolean isAccountNonExpired();

    boolean isAccountNonLocked();

    boolean isCredentialsNonExpired();

    boolean isEnabled();
}

public interface UserDetails extends Serializable {
    
    GrantedAuthority[] getAuthorities();

    String getPassword();

    String getUsername();

    boolean isAccountNonExpired();

    boolean isAccountNonLocked();

    boolean isCredentialsNonExpired();

    boolean isEnabled();
}

public interface UserDetailsService {
    UserDetails loadUserByUsername(String username)
        throws UsernameNotFoundException, DataAccessException;
}

public interface UserDetailsService {
    UserDetails loadUserByUsername(String username)
        throws UsernameNotFoundException, DataAccessException;
}

非常清楚，一個接口用於模擬用戶，另外一個用於模擬讀取用戶的過程。所以我們可以通過實現這兩個接口，來完成使用數據庫對用戶和權限進行管理的需求。在這裏，我將給出一個使用Hibernate來定義用戶和權限之間關係的示例。

1. 定義User類和Role類，使他們之間形成多對多的關係

@Entity
@Proxy(lazy = false)
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class User {

    private static final long serialVersionUID = 8026813053768023527L;

    @Id
    @GeneratedValue
    private Integer id;

    private String name;

    private String password;

    private boolean disabled;

    @ManyToMany(targetEntity = Role.class, fetch = FetchType.EAGER)
    @JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    private Set<Role> roles;

        // setters and getters
}

@Entity
@Proxy(lazy = false)
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class User {
	
	private static final long serialVersionUID = 8026813053768023527L;

    @Id
	@GeneratedValue
	private Integer id;
	
	private String name;
	
	private String password;
	
	private boolean disabled;
	
	@ManyToMany(targetEntity = Role.class, fetch = FetchType.EAGER)
    @JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
	private Set<Role> roles;

        // setters and getters
}

@Entity
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Role {

    @Id
    @GeneratedValue
    private Integer id;

    private String name;

        // setters and getters
}

@Entity
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Role {
	
	@Id
	@GeneratedValue
	private Integer id;
	
	private String name;
        
        // setters and getters
}

請注意這裏的Annotation的寫法。同時，我爲User和Role之間配置了緩存。並且將他們之間的關聯關係設置的lazy屬性設置成false，從而保證在User對象取出之後的使用不會因爲脫離session的生命週期而產生lazy loading問題。

2. 使User類實現UserDetails接口

接下來，我們讓User類去實現UserDetails接口：

@Entity
@Proxy(lazy = false)
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class User implements UserDetails {

    private static final long serialVersionUID = 8026813053768023527L;

    @Id
    @GeneratedValue
    private Integer id;

    private String name;

    private String password;

    private boolean disabled;

    @ManyToMany(targetEntity = Role.class, fetch = FetchType.EAGER)
    @JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    private Set<Role> roles;

    /**
     * The default constructor
     */
    public User() {

    }

    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetails#getAuthorities()
     */
    public GrantedAuthority[] getAuthorities() {
        List<GrantedAuthority> grantedAuthorities = new ArrayList<GrantedAuthority>(roles.size());
        for(Role role : roles) {
            grantedAuthorities.add(new GrantedAuthorityImpl(role.getName()));
        }
        return grantedAuthorities.toArray(new GrantedAuthority[roles.size()]);
    }

    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetails#getPassword()
     */
    public String getPassword() {
        return password;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetails#getUsername()
     */
    public String getUsername() {
        return name;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetails#isAccountNonExpired()
     */
    public boolean isAccountNonExpired() {
        return true;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetails#isAccountNonLocked()
     */
    public boolean isAccountNonLocked() {
        return true;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetails#isCredentialsNonExpired()
     */
    public boolean isCredentialsNonExpired() {
        return true;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetails#isEnabled()
     */
    public boolean isEnabled() {
        return !this.disabled;
    }

      // setters and getters
}

@Entity
@Proxy(lazy = false)
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class User implements UserDetails {
	
	private static final long serialVersionUID = 8026813053768023527L;

    @Id
	@GeneratedValue
	private Integer id;
	
	private String name;
	
	private String password;
	
	private boolean disabled;
	
	@ManyToMany(targetEntity = Role.class, fetch = FetchType.EAGER)
    @JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
	private Set<Role> roles;
	
	/**
	 * The default constructor
	 */
	public User() {
		
	}

	/* (non-Javadoc)
	 * @see org.springframework.security.userdetails.UserDetails#getAuthorities()
	 */
	public GrantedAuthority[] getAuthorities() {
		List<GrantedAuthority> grantedAuthorities = new ArrayList<GrantedAuthority>(roles.size());
    	for(Role role : roles) {
    		grantedAuthorities.add(new GrantedAuthorityImpl(role.getName()));
    	}
        return grantedAuthorities.toArray(new GrantedAuthority[roles.size()]);
	}

	/* (non-Javadoc)
	 * @see org.springframework.security.userdetails.UserDetails#getPassword()
	 */
	public String getPassword() {
		return password;
	}

	/* (non-Javadoc)
	 * @see org.springframework.security.userdetails.UserDetails#getUsername()
	 */
	public String getUsername() {
		return name;
	}

	/* (non-Javadoc)
	 * @see org.springframework.security.userdetails.UserDetails#isAccountNonExpired()
	 */
	public boolean isAccountNonExpired() {
		return true;
	}

	/* (non-Javadoc)
	 * @see org.springframework.security.userdetails.UserDetails#isAccountNonLocked()
	 */
	public boolean isAccountNonLocked() {
		return true;
	}

	/* (non-Javadoc)
	 * @see org.springframework.security.userdetails.UserDetails#isCredentialsNonExpired()
	 */
	public boolean isCredentialsNonExpired() {
		return true;
	}

	/* (non-Javadoc)
	 * @see org.springframework.security.userdetails.UserDetails#isEnabled()
	 */
	public boolean isEnabled() {
		return !this.disabled;
	}
      
      // setters and getters
}

實現UserDetails接口中的每個函數，其實沒什麼很大的難度，除了其中的一個函數我需要額外強調一下：

/* (non-Javadoc)
 * @see org.springframework.security.userdetails.UserDetails#getAuthorities()
 */
public GrantedAuthority[] getAuthorities() {
    List<GrantedAuthority> grantedAuthorities = new ArrayList<GrantedAuthority>(roles.size());
    for(Role role : roles) {
        grantedAuthorities.add(new GrantedAuthorityImpl(role.getName()));
        }
        return grantedAuthorities.toArray(new GrantedAuthority[roles.size()]);
}

/* (non-Javadoc)
 * @see org.springframework.security.userdetails.UserDetails#getAuthorities()
 */
public GrantedAuthority[] getAuthorities() {
	List<GrantedAuthority> grantedAuthorities = new ArrayList<GrantedAuthority>(roles.size());
   	for(Role role : roles) {
	    grantedAuthorities.add(new GrantedAuthorityImpl(role.getName()));
    	}
        return grantedAuthorities.toArray(new GrantedAuthority[roles.size()]);
}

這個函數的實際作用是根據User返回這個User所擁有的權限列表。如果以上面曾經用過的例子來說，如果當前User是downpour，我需要得到ROLE_USER和ROLE_ADMIN；如果當前User是robbin，我需要得到ROLE_USER。

瞭解了含義，實現就變得簡單了，由於User與Role是多對多的關係，我們可以通過User得到所有這個User所對應的Role，並把這些Role的name拼裝起來返回。

由此可見，實現UserDetails接口，並沒有什麼神祕的地方，它只是實際上在一定程度上只是代替了使用配置文件的硬編碼：

<user name="downpour" password="downpour" authorities="ROLE_USER, ROLE_ADMIN" />

<user name="downpour" password="downpour" authorities="ROLE_USER, ROLE_ADMIN" />

3. 實現UserDetailsService接口

@Repository("securityManager")
public class SecurityManagerSupport extends HibernateDaoSupport implements UserDetailsService {

    /**
     * Init sessionFactory here because the annotation of Spring 2.5 can not support override inject
     *
     * @param sessionFactory
     */
    @Autowired
    public void init(SessionFactory sessionFactory) {
        super.setSessionFactory(sessionFactory);
    }

    public UserDetails loadUserByUsername(String userName) throws UsernameNotFoundException, DataAccessException {
        List<User> users = getHibernateTemplate().find("FROM User user WHERE user.name = ? AND user.disabled = false", userName);
        if(users.isEmpty()) {
            throw new UsernameNotFoundException("User " + userName + " has no GrantedAuthority");
        }
        return users.get(0);
    }
}

@Repository("securityManager")
public class SecurityManagerSupport extends HibernateDaoSupport implements UserDetailsService {

    /**
     * Init sessionFactory here because the annotation of Spring 2.5 can not support override inject
     *  
     * @param sessionFactory
     */
    @Autowired
    public void init(SessionFactory sessionFactory) {
        super.setSessionFactory(sessionFactory);
    }

    public UserDetails loadUserByUsername(String userName) throws UsernameNotFoundException, DataAccessException {
        List<User> users = getHibernateTemplate().find("FROM User user WHERE user.name = ? AND user.disabled = false", userName);
        if(users.isEmpty()) {
            throw new UsernameNotFoundException("User " + userName + " has no GrantedAuthority");
        }
        return users.get(0);
    }
}

這個實現非常簡單，由於我們的User對象已經實現了UserDetails接口。所以我們只要使用Hibernate，根據userName取出相應的User對象即可。注意在這裏，由於我們對於User的關聯對象Roles都設置了lazy="false"，所以我們無需擔心lazy loading的問題。

4. 配置文件

有了上面的代碼，一切都變得很簡單，重新定義authentication-provider節點即可。如果你使用Spring 2.5的Annotation配置功能，你甚至可以不需要在配置文件中定義securityManager的bean。

<authentication-provider user-service-ref="securityManager">
    <password-encoder hash="md5"/>
</authentication-provider>

<authentication-provider user-service-ref="securityManager">
	<password-encoder hash="md5"/>
</authentication-provider>

使用數據庫對資源進行管理

在完成了使用數據庫來進行用戶和權限的管理之後，我們再來看看http配置的部分。在實際應用中，我們不可能使用類似/**的方式來指定URL與權限ROLE的對應關係，而是會針對某些URL，指定某些特定的ROLE。而URL與ROLE之間的映射關係最好可以進行擴展和配置。而URL屬於資源的一種，所以接下來，我們就來看看如何使用數據庫來對權限和資源的匹配關係進行管理，並且將認證匹配加入到Spring Security中去。

權限和資源的設計

上面我們講到，用戶（User）和權限（Role）之間是一個多對多的關係。那麼權限（Role）和資源（Resource）之間呢？其實他們之間也是一個典型的多對多的關係，我們同樣用3張表來表示：

CREATE TABLE `role` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) default NULL,
  `description` varchar(255) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `resource` (
  `id` int(11) NOT NULL auto_increment,
  `type` varchar(255) default NULL,
  `value` varchar(255) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `role_resource` (
  `role_id` int(11) NOT NULL,
  `resource_id` int(11) NOT NULL,
  PRIMARY KEY  (`role_id`,`resource_id`),
  KEY `FKAEE599B751827FA1` (`role_id`),
  KEY `FKAEE599B7EFD18D21` (`resource_id`),
  CONSTRAINT `FKAEE599B751827FA1` FOREIGN KEY (`role_id`) REFERENCES `role` (`id`),
  CONSTRAINT `FKAEE599B7EFD18D21` FOREIGN KEY (`resource_id`) REFERENCES `resource` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `role` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) default NULL,
  `description` varchar(255) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `resource` (
  `id` int(11) NOT NULL auto_increment,
  `type` varchar(255) default NULL,
  `value` varchar(255) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `role_resource` (
  `role_id` int(11) NOT NULL,
  `resource_id` int(11) NOT NULL,
  PRIMARY KEY  (`role_id`,`resource_id`),
  KEY `FKAEE599B751827FA1` (`role_id`),
  KEY `FKAEE599B7EFD18D21` (`resource_id`),
  CONSTRAINT `FKAEE599B751827FA1` FOREIGN KEY (`role_id`) REFERENCES `role` (`id`),
  CONSTRAINT `FKAEE599B7EFD18D21` FOREIGN KEY (`resource_id`) REFERENCES `resource` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

在這裏Resource可能分成多種類型，比如MENU,URL,METHOD等等。

針對資源的認證

針對資源的認證，實際上應該由Spring Security中的FilterSecurityInterceptor這個過濾器來完成。不過內置的FilterSecurityInterceptor的實現往往無法滿足我們的要求，所以傳統的Acegi的方式，我們往往會替換FilterSecurityInterceptor的實現，從而對URL等資源進行認證。

不過在Spring Security中，由於默認的攔截器鏈內置了FilterSecurityInterceptor，而且上面我們也提到過，這個實現無法被替換。這就使我們犯了難。我們如何對資源進行認證呢？

實際上，我們雖然無法替換FilterSecurityInterceptor的默認實現，不過我們可以再實現一個類似的過濾器，並將我們自己的過濾器作爲一個customer-filter，加到默認的過濾器鏈的最後，從而完成整個過濾檢查。

接下來我們就來看看一個完整的例子：

1. 建立權限（Role）和資源（Resource）之間的關聯關係

修改上面的權限（Role）的Entity定義：

@Entity
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Role {

    @Id
    @GeneratedValue
    private Integer id;

    private String name;

    @ManyToMany(targetEntity = Resource.class, fetch = FetchType.EAGER)
    @JoinTable(name = "role_resource", joinColumns = @JoinColumn(name = "role_id"), inverseJoinColumns = @JoinColumn(name = "resource_id"))
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    private Set<Resource> resources;

        // setters and getter
}

@Entity
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Role {
	
	@Id
	@GeneratedValue
	private Integer id;
	
	private String name;
	
	@ManyToMany(targetEntity = Resource.class, fetch = FetchType.EAGER)
    @JoinTable(name = "role_resource", joinColumns = @JoinColumn(name = "role_id"), inverseJoinColumns = @JoinColumn(name = "resource_id"))
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
	private Set<Resource> resources;

        // setters and getter
}

增加資源（Resource）的Entity定義：

@Entity
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)

public class Resource {

    @Id
    @GeneratedValue
    private Integer id;

    private String type;

    private String value;

    @ManyToMany(mappedBy = "resources", targetEntity = Role.class, fetch = FetchType.EAGER)
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    private Set<Role> roles;

    /**
     * The default constructor
     */
    public Resource() {

    }
}

@Entity
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)

public class Resource {

	@Id
    @GeneratedValue
	private Integer id;
	
	private String type;
	
	private String value;
	
	@ManyToMany(mappedBy = "resources", targetEntity = Role.class, fetch = FetchType.EAGER)
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
	private Set<Role> roles;
	
	/**
	 * The default constructor
	 */
	public Resource() {
		
	}
}

注意他們之間的多對多關係，以及他們之間關聯關係的緩存和lazy屬性設置。

2. 在系統啓動的時候，把所有的資源load到內存作爲緩存

由於資源信息對於每個項目來說，相對固定，所以我們可以將他們在系統啓動的時候就load到內存作爲緩存。這裏做法很多，我給出的示例是將資源的存放在servletContext中。

public class ServletContextLoaderListener implements ServletContextListener {

    /* (non-Javadoc)
     * @see javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)
     */
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();
        SecurityManager securityManager = this.getSecurityManager(servletContext);

        Map<String, String> urlAuthorities = securityManager.loadUrlAuthorities();
        servletContext.setAttribute("urlAuthorities", urlAuthorities);
    }


    /* (non-Javadoc)
     * @see javax.servlet.ServletContextListener#contextDestroyed(javax.servlet.ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        servletContextEvent.getServletContext().removeAttribute("urlAuthorities");
    }

    /**
     * Get SecurityManager from ApplicationContext
     *
     * @param servletContext
     * @return
     */
    protected SecurityManager getSecurityManager(ServletContext servletContext) {
       return (SecurityManager) WebApplicationContextUtils.getWebApplicationContext(servletContext).getBean("securityManager");
    }

}

public class ServletContextLoaderListener implements ServletContextListener {

    /* (non-Javadoc)
     * @see javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)
     */
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();
        SecurityManager securityManager = this.getSecurityManager(servletContext);
        
        Map<String, String> urlAuthorities = securityManager.loadUrlAuthorities();
        servletContext.setAttribute("urlAuthorities", urlAuthorities);
    }

    
    /* (non-Javadoc)
     * @see javax.servlet.ServletContextListener#contextDestroyed(javax.servlet.ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        servletContextEvent.getServletContext().removeAttribute("urlAuthorities");
    }

    /**
     * Get SecurityManager from ApplicationContext
     * 
     * @param servletContext
     * @return
     */
    protected SecurityManager getSecurityManager(ServletContext servletContext) {
       return (SecurityManager) WebApplicationContextUtils.getWebApplicationContext(servletContext).getBean("securityManager"); 
    }

}

這裏，我們看到了SecurityManager，這是一個接口，用於權限相關的邏輯處理。還記得之前我們使用數據庫管理User的時候所使用的一個實現類SecurityManagerSupport嘛？我們不妨依然借用這個類，讓它實現SecurityManager接口，來同時完成url的讀取工作。

@Service("securityManager")
public class SecurityManagerSupport extends HibernateDaoSupport implements UserDetailsService, SecurityManager {

    /**
     * Init sessionFactory here because the annotation of Spring 2.5 can not support override inject
     *
     * @param sessionFactory
     */
    @Autowired
    public void init(SessionFactory sessionFactory) {
        super.setSessionFactory(sessionFactory);
    }

    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetailsService#loadUserByUsername(java.lang.String)
     */
    public UserDetails loadUserByUsername(String userName) throws UsernameNotFoundException, DataAccessException {
        List<User> users = getHibernateTemplate().find("FROM User user WHERE user.name = ? AND user.disabled = false", userName);
        if(users.isEmpty()) {
            throw new UsernameNotFoundException("User " + userName + " has no GrantedAuthority");
        }
        return users.get(0);
    }

    /* (non-Javadoc)
     * @see com.javaeye.sample.security.SecurityManager#loadUrlAuthorities()
     */
    public Map<String, String> loadUrlAuthorities() {
        Map<String, String> urlAuthorities = new HashMap<String, String>();
        List<Resource> urlResources = getHibernateTemplate().find("FROM Resource resource WHERE resource.type = ?", "URL");
        for(Resource resource : urlResources) {
            urlAuthorities.put(resource.getValue(), resource.getRoleAuthorities());
        }
        return urlAuthorities;
    }
}

@Service("securityManager")
public class SecurityManagerSupport extends HibernateDaoSupport implements UserDetailsService, SecurityManager {
    
    /**
     * Init sessionFactory here because the annotation of Spring 2.5 can not support override inject
     *  
     * @param sessionFactory
     */
    @Autowired
    public void init(SessionFactory sessionFactory) {
        super.setSessionFactory(sessionFactory);
    }
    
    /* (non-Javadoc)
     * @see org.springframework.security.userdetails.UserDetailsService#loadUserByUsername(java.lang.String)
     */
    public UserDetails loadUserByUsername(String userName) throws UsernameNotFoundException, DataAccessException {
        List<User> users = getHibernateTemplate().find("FROM User user WHERE user.name = ? AND user.disabled = false", userName);
        if(users.isEmpty()) {
            throw new UsernameNotFoundException("User " + userName + " has no GrantedAuthority");
        }
        return users.get(0);
    }
    
    /* (non-Javadoc)
     * @see com.javaeye.sample.security.SecurityManager#loadUrlAuthorities()
     */
    public Map<String, String> loadUrlAuthorities() {
        Map<String, String> urlAuthorities = new HashMap<String, String>();
        List<Resource> urlResources = getHibernateTemplate().find("FROM Resource resource WHERE resource.type = ?", "URL");
        for(Resource resource : urlResources) {
            urlAuthorities.put(resource.getValue(), resource.getRoleAuthorities());
        }
        return urlAuthorities;
    }   
}

3. 編寫自己的FilterInvocationDefinitionSource實現類，對資源進行認證

public class SecureResourceFilterInvocationDefinitionSource implements FilterInvocationDefinitionSource, InitializingBean {

    private UrlMatcher urlMatcher;

    private boolean useAntPath = true;

    private boolean lowercaseComparisons = true;

    /**
     * @param useAntPath the useAntPath to set
     */
    public void setUseAntPath(boolean useAntPath) {
        this.useAntPath = useAntPath;
    }

    /**
     * @param lowercaseComparisons
     */
    public void setLowercaseComparisons(boolean lowercaseComparisons) {
        this.lowercaseComparisons = lowercaseComparisons;
    }

    /* (non-Javadoc)
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
     */
    public void afterPropertiesSet() throws Exception {

        // default url matcher will be RegexUrlPathMatcher
        this.urlMatcher = new RegexUrlPathMatcher();

        if (useAntPath) {  // change the implementation if required
            this.urlMatcher = new AntUrlPathMatcher();
        }

        // Only change from the defaults if the attribute has been set
        if ("true".equals(lowercaseComparisons)) {
            if (!this.useAntPath) {
                ((RegexUrlPathMatcher) this.urlMatcher).setRequiresLowerCaseUrl(true);
            }
        } else if ("false".equals(lowercaseComparisons)) {
            if (this.useAntPath) {
                ((AntUrlPathMatcher) this.urlMatcher).setRequiresLowerCaseUrl(false);
            }
        }

    }

    /* (non-Javadoc)
     * @see org.springframework.security.intercept.ObjectDefinitionSource#getAttributes(java.lang.Object)
     */
    public ConfigAttributeDefinition getAttributes(Object filter) throws IllegalArgumentException {

        FilterInvocation filterInvocation = (FilterInvocation) filter;
        String requestURI = filterInvocation.getRequestUrl();
        Map<String, String> urlAuthorities = this.getUrlAuthorities(filterInvocation);

        String grantedAuthorities = null;
        for(Iterator<Map.Entry<String, String>> iter = urlAuthorities.entrySet().iterator(); iter.hasNext();) {
            Map.Entry<String, String> entry = iter.next();
            String url = entry.getKey();

            if(urlMatcher.pathMatchesUrl(url, requestURI)) {
                grantedAuthorities = entry.getValue();
                break;
            }

        }

        if(grantedAuthorities != null) {
            ConfigAttributeEditor configAttrEditor = new ConfigAttributeEditor();
            configAttrEditor.setAsText(grantedAuthorities);
            return (ConfigAttributeDefinition) configAttrEditor.getValue();
        }

        return null;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.intercept.ObjectDefinitionSource#getConfigAttributeDefinitions()
     */
    @SuppressWarnings("unchecked")
    public Collection getConfigAttributeDefinitions() {
        return null;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.intercept.ObjectDefinitionSource#supports(java.lang.Class)
     */
    @SuppressWarnings("unchecked")
    public boolean supports(Class clazz) {
        return true;
    }

    /**
     *
     * @param filterInvocation
     * @return
     */
    @SuppressWarnings("unchecked")
    private Map<String, String> getUrlAuthorities(FilterInvocation filterInvocation) {
        ServletContext servletContext = filterInvocation.getHttpRequest().getSession().getServletContext();
        return (Map<String, String>)servletContext.getAttribute("urlAuthorities");
    }

}

public class SecureResourceFilterInvocationDefinitionSource implements FilterInvocationDefinitionSource, InitializingBean {
    
    private UrlMatcher urlMatcher;

    private boolean useAntPath = true;
    
    private boolean lowercaseComparisons = true;
    
    /**
     * @param useAntPath the useAntPath to set
     */
    public void setUseAntPath(boolean useAntPath) {
        this.useAntPath = useAntPath;
    }
    
    /**
     * @param lowercaseComparisons
     */
    public void setLowercaseComparisons(boolean lowercaseComparisons) {
        this.lowercaseComparisons = lowercaseComparisons;
    }
    
    /* (non-Javadoc)
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet()
     */
    public void afterPropertiesSet() throws Exception {
        
        // default url matcher will be RegexUrlPathMatcher
        this.urlMatcher = new RegexUrlPathMatcher();
        
        if (useAntPath) {  // change the implementation if required
            this.urlMatcher = new AntUrlPathMatcher();
        }
        
        // Only change from the defaults if the attribute has been set
        if ("true".equals(lowercaseComparisons)) {
            if (!this.useAntPath) {
                ((RegexUrlPathMatcher) this.urlMatcher).setRequiresLowerCaseUrl(true);
            }
        } else if ("false".equals(lowercaseComparisons)) {
            if (this.useAntPath) {
                ((AntUrlPathMatcher) this.urlMatcher).setRequiresLowerCaseUrl(false);
            }
        }
        
    }
    
    /* (non-Javadoc)
     * @see org.springframework.security.intercept.ObjectDefinitionSource#getAttributes(java.lang.Object)
     */
    public ConfigAttributeDefinition getAttributes(Object filter) throws IllegalArgumentException {
        
        FilterInvocation filterInvocation = (FilterInvocation) filter;
        String requestURI = filterInvocation.getRequestUrl();
        Map<String, String> urlAuthorities = this.getUrlAuthorities(filterInvocation);
        
        String grantedAuthorities = null;
        for(Iterator<Map.Entry<String, String>> iter = urlAuthorities.entrySet().iterator(); iter.hasNext();) {
            Map.Entry<String, String> entry = iter.next();
            String url = entry.getKey();
            
            if(urlMatcher.pathMatchesUrl(url, requestURI)) {
                grantedAuthorities = entry.getValue();
                break;
            }
            
        }
        
        if(grantedAuthorities != null) {
            ConfigAttributeEditor configAttrEditor = new ConfigAttributeEditor();
            configAttrEditor.setAsText(grantedAuthorities);
            return (ConfigAttributeDefinition) configAttrEditor.getValue();
        }
        
        return null;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.intercept.ObjectDefinitionSource#getConfigAttributeDefinitions()
     */
    @SuppressWarnings("unchecked")
	public Collection getConfigAttributeDefinitions() {
        return null;
    }

    /* (non-Javadoc)
     * @see org.springframework.security.intercept.ObjectDefinitionSource#supports(java.lang.Class)
     */
    @SuppressWarnings("unchecked")
	public boolean supports(Class clazz) {
        return true;
    }
    
    /**
     * 
     * @param filterInvocation
     * @return
     */
    @SuppressWarnings("unchecked")
	private Map<String, String> getUrlAuthorities(FilterInvocation filterInvocation) {
        ServletContext servletContext = filterInvocation.getHttpRequest().getSession().getServletContext();
        return (Map<String, String>)servletContext.getAttribute("urlAuthorities");
    }

}

4. 配置文件修改

接下來，我們來修改一下Spring Security的配置文件，把我們自定義的這個過濾器插入到過濾器鏈中去。

<beans:beans xmlns="http://www.springframework.org/schema/security"
    xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
                        http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security-2.0.4.xsd">

    <beans:bean id="loggerListener" class="org.springframework.security.event.authentication.LoggerListener" />

    <http access-denied-page="/403.jsp" >
        <intercept-url pattern="/static/**" filters="none" />
        <intercept-url pattern="/template/**" filters="none" />
        <intercept-url pattern="/" filters="none" />
        <intercept-url pattern="/login.jsp" filters="none" />
        <form-login login-page="/login.jsp" authentication-failure-url="/login.jsp?error=true" default-target-url="/index" />
        <logout logout-success-url="/login.jsp"/>
        <http-basic />
    </http>

    <authentication-manager alias="authenticationManager"/>

    <authentication-provider user-service-ref="securityManager">
        <password-encoder hash="md5"/>
    </authentication-provider>

    <beans:bean id="accessDecisionManager" class="org.springframework.security.vote.AffirmativeBased">
        <beans:property name="allowIfAllAbstainDecisions" value="false"/>
        <beans:property name="decisionVoters">
            <beans:list>
                <beans:bean class="org.springframework.security.vote.RoleVoter"/>
                <beans:bean class="org.springframework.security.vote.AuthenticatedVoter"/>
            </beans:list>
        </beans:property>
    </beans:bean>

    <beans:bean id="resourceSecurityInterceptor" class="org.springframework.security.intercept.web.FilterSecurityInterceptor">
        <beans:property name="authenticationManager" ref="authenticationManager"/>
        <beans:property name="accessDecisionManager" ref="accessDecisionManager"/>
        <beans:property name="objectDefinitionSource" ref="secureResourceFilterInvocationDefinitionSource" />
        <beans:property name="observeOncePerRequest" value="false" />
        <custom-filter after="LAST" />
    </beans:bean>

    <beans:bean id="secureResourceFilterInvocationDefinitionSource" class="com.javaeye.sample.security.interceptor.SecureResourceFilterInvocationDefinitionSource" />

</beans:beans>

<beans:beans xmlns="http://www.springframework.org/schema/security"
    xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
                        http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security-2.0.4.xsd">
	
	<beans:bean id="loggerListener" class="org.springframework.security.event.authentication.LoggerListener" />
	
	<http access-denied-page="/403.jsp" >
		<intercept-url pattern="/static/**" filters="none" />
		<intercept-url pattern="/template/**" filters="none" />
		<intercept-url pattern="/" filters="none" />
		<intercept-url pattern="/login.jsp" filters="none" />
	    <form-login login-page="/login.jsp" authentication-failure-url="/login.jsp?error=true" default-target-url="/index" />
	    <logout logout-success-url="/login.jsp"/>
	    <http-basic />
	</http>

	<authentication-manager alias="authenticationManager"/>
	
	<authentication-provider user-service-ref="securityManager">
		<password-encoder hash="md5"/>
	</authentication-provider>
	
	<beans:bean id="accessDecisionManager" class="org.springframework.security.vote.AffirmativeBased">
	    <beans:property name="allowIfAllAbstainDecisions" value="false"/>
	    <beans:property name="decisionVoters">
	        <beans:list>
	            <beans:bean class="org.springframework.security.vote.RoleVoter"/>
	            <beans:bean class="org.springframework.security.vote.AuthenticatedVoter"/>
	        </beans:list>
	    </beans:property>
	</beans:bean>
	
	<beans:bean id="resourceSecurityInterceptor" class="org.springframework.security.intercept.web.FilterSecurityInterceptor">
		<beans:property name="authenticationManager" ref="authenticationManager"/>
	    <beans:property name="accessDecisionManager" ref="accessDecisionManager"/>
	    <beans:property name="objectDefinitionSource" ref="secureResourceFilterInvocationDefinitionSource" />
	    <beans:property name="observeOncePerRequest" value="false" />
	    <custom-filter after="LAST" />
	</beans:bean>
	
	<beans:bean id="secureResourceFilterInvocationDefinitionSource" class="com.javaeye.sample.security.interceptor.SecureResourceFilterInvocationDefinitionSource" />
	
</beans:beans>

請注意，由於我們所實現的，是FilterSecurityInterceptor中的一個開放接口，所以我們實際上定義了一個新的bean，並通過<custom-filter after="LAST" />插入到過濾器鏈中去。

Spring Security對象的訪問

1. 訪問當前登錄用戶

Spring Security提供了一個線程安全的對象：SecurityContextHolder，通過這個對象，我們可以訪問當前的登錄用戶。我寫了一個類，可以通過靜態方法去讀取：

public class SecurityUserHolder {

    /**
     * Returns the current user
     *
     * @return
     */
    public static User getCurrentUser() {
        return (User) SecurityContextHolder.getContext().getAuthentication().getPrincipal();
    }

}

public class SecurityUserHolder {

	/**
	 * Returns the current user
	 * 
	 * @return
	 */
	public static User getCurrentUser() {
		return (User) SecurityContextHolder.getContext().getAuthentication().getPrincipal();
	}

}

2. 訪問當前登錄用戶所擁有的權限

通過上面的分析，我們知道，用戶所擁有的所有權限，其實是通過UserDetails接口中的getAuthorities()方法獲得的。只要實現這個接口，就能實現需求。在我的代碼中，不僅實現了這個接口，還在上面做了點小文章，這樣我們可以獲得一個用戶所擁有權限的字符串表示：

/* (non-Javadoc)
 * @see org.springframework.security.userdetails.UserDetails#getAuthorities()
 */
public GrantedAuthority[] getAuthorities() {
    List<GrantedAuthority> grantedAuthorities = new ArrayList<GrantedAuthority>(roles.size());
    for(Role role : roles) {
        grantedAuthorities.add(new GrantedAuthorityImpl(role.getName()));
    }
       return grantedAuthorities.toArray(new GrantedAuthority[roles.size()]);
}

/**
 * Returns the authorites string
 *
 * eg.
 *    downpour --- ROLE_ADMIN,ROLE_USER
 *    robbin --- ROLE_ADMIN
 *
 * @return
 */
public String getAuthoritiesString() {
    List<String> authorities = new ArrayList<String>();
    for(GrantedAuthority authority : this.getAuthorities()) {
        authorities.add(authority.getAuthority());
    }
    return StringUtils.join(authorities, ",");
}

	/* (non-Javadoc)
	 * @see org.springframework.security.userdetails.UserDetails#getAuthorities()
	 */
	public GrantedAuthority[] getAuthorities() {
		List<GrantedAuthority> grantedAuthorities = new ArrayList<GrantedAuthority>(roles.size());
    	for(Role role : roles) {
    		grantedAuthorities.add(new GrantedAuthorityImpl(role.getName()));
    	}
        return grantedAuthorities.toArray(new GrantedAuthority[roles.size()]);
	}
	
	/**
	 * Returns the authorites string
	 * 
	 * eg. 
	 *    downpour --- ROLE_ADMIN,ROLE_USER
	 *    robbin --- ROLE_ADMIN
	 * 
	 * @return
	 */
	public String getAuthoritiesString() {
	    List<String> authorities = new ArrayList<String>();
	    for(GrantedAuthority authority : this.getAuthorities()) {
	        authorities.add(authority.getAuthority());
	    }
	    return StringUtils.join(authorities, ",");
	}

3. 訪問當前登錄用戶能夠訪問的資源

這就涉及到用戶（User），權限（Role）和資源（Resource）三者之間的對應關係。我同樣在User對象中實現了一個方法：

/**
 * @return the roleResources
 */
public Map<String, List<Resource>> getRoleResources() {
    // init roleResources for the first time
    if(this.roleResources == null) {
        this.roleResources = new HashMap<String, List<Resource>>();

        for(Role role : this.roles) {
            String roleName = role.getName();
            Set<Resource> resources = role.getResources();
            for(Resource resource : resources) {
                String key = roleName + "_" + resource.getType();
                    if(!this.roleResources.containsKey(key)) {
                        this.roleResources.put(key, new ArrayList<Resource>());
                }
                    this.roleResources.get(key).add(resource);
            }
        }

    }
    return this.roleResources;
}

/**
 * @return the roleResources
 */
public Map<String, List<Resource>> getRoleResources() {
	// init roleResources for the first time
	if(this.roleResources == null) {			
		this.roleResources = new HashMap<String, List<Resource>>();
			
		for(Role role : this.roles) {
			String roleName = role.getName();
			Set<Resource> resources = role.getResources();
			for(Resource resource : resources) {
				String key = roleName + "_" + resource.getType();
					if(!this.roleResources.containsKey(key)) {
						this.roleResources.put(key, new ArrayList<Resource>());
				}
					this.roleResources.get(key).add(resource);					
			}
		}
			
	}
	return this.roleResources;
}

這裏，會在User對象中設置一個緩存機制，在第一次取的時候，通過遍歷User所有的Role，獲取相應的Resource信息。

代碼示例