SpringBoot（二）：Spring的JAVA配置方式

說明：Java配置是Spring4.x推薦的配置方式，可以完全替代xml配置。

1.重要註解@Configuration和@Bean

    1.1@Configuration作用於類上，相當於一個xml配置文件；

    1.2@Bean作用於方法上，相當於xml配置中的<bean>；

2.示例

    該示例演示了通過Java配置的方式進行配置Spring，並且實現了Spring IOC功能。

    2.1創建工程以及導入依賴

       2.1.1pom.xml文件配置：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>cn.itcast.springboot</groupId>
	<artifactId>itcast-springboot</artifactId>
	<version>1.0.0-SNAPSHOT</version>
	<packaging>war</packaging>

	<dependencies>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>4.3.7.RELEASE</version>
		</dependency>
		<!-- 連接池 -->
		<dependency>
			<groupId>com.jolbox</groupId>
			<artifactId>bonecp-spring</artifactId>
			<version>0.8.0.RELEASE</version>
		</dependency>
	</dependencies>
	<build>
		<finalName>${project.artifactId}</finalName>
		<plugins>
			<!-- 資源文件拷貝插件 -->
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-resources-plugin</artifactId>
				<configuration>
					<encoding>UTF-8</encoding>
				</configuration>
			</plugin>
			<!-- java編譯插件 -->
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<source>1.7</source>
					<target>1.7</target>
					<encoding>UTF-8</encoding>
				</configuration>
			</plugin>
		</plugins>
		<pluginManagement>
			<plugins>
				<!-- 配置Tomcat插件 -->
				<plugin>
					<groupId>org.apache.tomcat.maven</groupId>
					<artifactId>tomcat7-maven-plugin</artifactId>
					<version>2.2</version>
				</plugin>
			</plugins>
		</pluginManagement>
	</build>
</project>

    2.2創建User實體類

public class User {

    private String username;

    private String password;

    private Integer age;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

}

    2.3創建UserDao類用於模擬與數據庫的交互

public class UserDAO {
    
    public List<User> queryUserList(){
        List<User> result = new ArrayList<User>();
        // 模擬數據庫的查詢
        for (int i = 0; i < 10; i++) {
            User user = new User();
            user.setUsername("username_" + i);
            user.setPassword("password_" + i);
            user.setAge(i + 1);
            result.add(user);
        }
        return result;
    }

}

    2.4創建UserService類用於實現User數據操作業務邏輯

@Service
public class UserService {

    @Autowired // 注入Spring容器中的bean對象
    private UserDAO userDAO;

    public List<User> queryUserList() {
        // 調用userDAO中的方法進行查詢
        return this.userDAO.queryUserList();
    }

}

    2.5創建SpringConfig類用戶實例化Spring容器

@Configuration //通過該註解來表明該類是一個Spring的配置，相當於一個xml文件
@ComponentScan(basePackages = "cn.itcast.springboot.javaconfig") //配置掃描包
public class SpringConfig {
    
    @Bean // 通過該註解來表明是一個Bean對象，相當於xml中的<bean>
    public UserDAO getUserDAO(){
        return new UserDAO(); // 直接new對象做演示
    }
    
}

    2.6編寫測試方法用於啓動Spring容器

public class Main {
    
    public static void main(String[] args) {
        // 通過Java配置來實例化Spring容器
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
        
        // 在Spring容器中獲取Bean對象
        UserService userService = context.getBean(UserService.class);
        
        // 調用對象中的方法
        List<User> list = userService.queryUserList();
        for (User user : list) {
            System.out.println(user.getUsername() + ", " + user.getPassword() + ", " + user.getPassword());
        }
        
        // 銷燬該容器
        context.destroy();
    }

}

    2.7測試效果

username_0, password_0, password_0
username_1, password_1, password_1
username_2, password_2, password_2
username_3, password_3, password_3
username_4, password_4, password_4
username_5, password_5, password_5
username_6, password_6, password_6
username_7, password_7, password_7
username_8, password_8, password_8
username_9, password_9, password_9