SpringBoot Web（下）

什麼是Servlet？

Servlet是一種基於Java技術的Web組件，用於生成動態內容，由容器管理。類似於其他Java技術組件，Servlet是平臺無關的Java類組成，並且由Java Web服務器加載執行

什麼是Servlet容器？

Servlet 容器，有時候也稱作爲 Servlet 引擎，作爲Web服務器或應用服務器的一部分。通過請求和響應對話，提供 Web 客戶端與 Servlets 交互的能力。容器管理Servlets實例以及它們的生命週期。

Servlet 3.0前時代

服務組件

• javax.servlet.Servlet
• javax.servlet.Filter（since Servlet 2.3）

上下文組件

• javax.servlet.ServletContext
• javax.servlet.http.HttpSession（服務端）
• javax.servlet.http.HttpServletRequest
• javax.servlet.http.HttpServletResponse
• javax.servlet.http.Cookie（客戶端）

配置

• javax.servlet.ServletConfig
• javax.servlet.FilterConfig（since Servlet 2.3 ）

輸入輸出（二進制輸入和輸出）

• javax.servlet.ServletInputStream
• javax.servlet.ServletOutputStream

異常

• javax.servlet.ServletException

事件

生命週期類型

• javax.servlet.ServletContextEvent
• javax.servlet.http.HttpSessionEvent
• java.servlet.ServletRequestEvent

屬性上下文類型

• javax.servlet.ServletContextAttributeEvent
• javax.servlet.http.HttpSessionBindingEvent
• javax.servlet.ServletRequestAttributeEvent

監聽器（since Servlet 2.3）

生命週期類型

• javax.servlet.ServletContextListener
• javax.servlet.http.HttpSessionListener
• javax.servlet.http.HttpSessionActivationListener
• javax.servlet.ServletRequestListener

屬性上下文類型

• javax.servlet.ServletContextAttributeListener
• javax.servlet.http.HttpSessionAttributeListener
• javax.servlet.http.HttpSessionBindingListener
• javax.servlet.ServletRequestAttributeListener

Servlet 3.0後時代

組件申明註解

@javax.servlet.annotation.WebServlet
@javax.servlet.annotation.WebFilter
@javax.servlet.annotation.WebListener
下面是權限和安全
@javax.servlet.annotation.ServletSecurity
@javax.servlet.annotation.HttpMethodConstraint
@javax.servlet.annotation.HttpConstraint

配置申明

@javax.servlet.annotation.WebInitParam

上下文

javax.servlet.AsyncContext

事件

javax.servlet.AsyncEvent

監聽器

javax.servlet.AsyncListener

Servlet 組件註冊

javax.servlet.ServletContext#addServlet()
javax.servlet.ServletRegistration

Filter 組件註冊

javax.servlet.ServletContext#addFilter()
javax.servlet.FilterRegistration

監聽器註冊

javax.servlet.ServletContext#addListener()
javax.servlet.AsyncListener

自動裝配

初始器
javax.servlet.ServletContainerInitializer

類型過濾
@javax.servlet.annotation.HandlesTypes

Servlet 生命週期

一般情況不會直接實現Servlet接口，而是繼承HttpServlet接口，他的service方法會獲取當前http請求的方法，然後調用對應的doGet/doHead/doPost/doPut/doDelete/doOptions方法

初始化
當容器啓動或者第一次執行時，Servlet#init(ServletConfig)方法被執行，初始化當前Servlet 。

處理請求
當HTTP 請求到達容器時，Servlet#service(ServletRequest,ServletResponse) 方法被執行，來處理請求。

銷燬
當容器關閉時，容器將會調用Servlet#destroy 方法被執行，銷燬當前Servlet。

Filter 生命週期

初始化
當容器啓動時，Filter#init(FilterConfig)方法被執行，初始化當前Filter。

處理請求
當HTTP 請求到達容器時，Filter#doFilter(ServletRequest,ServletResponse,FilterChain) 方法被執行，來攔截請求，在Servlet#service(ServletRequest,ServletResponse) 方法調用前執行。

銷燬
當容器關閉時，容器將會調用Filter#destroy 方法被執行，銷燬當前Filter。

Servlet On Spring Boot

Servlet 組件掃描

@org.springframework.boot.web.servlet.ServletComponentScan
指定包路徑掃描
String[] value() default {}
String[] basePackages() default {}

指定類掃描
Class<?>[] basePackageClasses() default {}

註解方式註冊

Servlet組件

1.擴展 javax.servlet.Servlet
javax.servlet.http.HttpServlet
org.springframework.web.servlet.FrameworkServlet

2.標記 @javax.servlet.annotation.WebServlet
Servlet

Filter組件

實現 javax.servlet.Filter
org.springframework.web.filter.OncePerRequestFilter


標記 @javax.servlet.annotation.WebFilter

監聽器

監聽器組件
實現Listener接口
javax.servlet.ServletContextListener
javax.servlet.http.HttpSessionListener
javax.servlet.http.HttpSessionActivationListener
javax.servlet.ServletRequestListener
javax.servlet.ServletContextAttributeListener
javax.servlet.http.HttpSessionAttributeListener
javax.servlet.http.HttpSessionBindingListener
javax.servlet.ServletRequestAttributeListener
標記 @javax.servlet.annotation.WebListener

SpringBootLearnApplication

@SpringBootApplication
@ServletComponentScan(basePackages = {"com.yun.springbootlearn.servlet"})
public class SpringBootLearnApplication extends SpringBootServletInitializer {

	public static void main(String[] args) {
		SpringApplication.run(SpringBootLearnApplication.class, args);
		System.out.println("start");
	}

}

MyFilter

@WebFilter(urlPatterns = "/myservlet")
public class MyFilter extends OncePerRequestFilter {

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {

        ServletContext context = request.getServletContext();

        context.log("/myservlet was filtered");
        filterChain.doFilter(request,response);


    }
}

MyServlet

@WebServlet(
        name = "myServlet",
        urlPatterns = "/myservlet",
        initParams ={
                @WebInitParam(name = "myname", value = "myvalue")
        }
)
public class MyServlet extends HttpServlet {

    private String value;

    @Override
    public void init(ServletConfig servletConfig) throws ServletException {
        super.init(servletConfig);
        value = servletConfig.getInitParameter("myname");
    }


    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Writer writer = resp.getWriter();
        //是通過super.init(servletConfig)初始化好纔可以得到ServletContent
        ServletContext context = getServletContext();
        context.log("myServlet do get");

        writer.write("<html><body>Hello,World“”“"+value+"</body></html>");
    }
}


MyListener

@WebListener
public class MyServletRequestListener implements ServletRequestListener {

    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        HttpServletRequest request = (HttpServletRequest) sre.getServletRequest();
        ServletContext context = request.getServletContext();
        context.log("request was initialized");
    }

    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        HttpServletRequest request = (HttpServletRequest) sre.getServletRequest();
        ServletContext context = request.getServletContext();
        context.log("request was destoryed");
    }

}

Spring Boot API方式註冊

Servlet 組件

1.擴展 javax.servlet.Servlet
javax.servlet.http.HttpServlet
org.springframework.web.servlet.FrameworkServlet
2.組裝 Servlet
 Spring Boot 1.4.0 開始支持
org.springframework.boot.web.servlet.ServletRegistrationBean
Spring Boot  1.4.0 之前
org.springframework.boot.context.embedded.ServletRegistrationBean
3.暴露 Spring Bean
@Bean

Filter 組件

1.實現 javax.servlet.Filter
org.springframework.web.filter.OncePerRequestFilter
2.組裝 Filter
 Spring Boot 1.4.0 開始
org.springframework.boot.web.servlet.FilterRegistrationBean
Spring Boot  1.4.0 之前
org.springframework.boot.context.embedded.FilterRegistrationBean
3.暴露 Spring Bean
@Bean

監聽器組件

1.實現 Listener
2.組裝 Listener
 Spring Boot 1.4.0 開始
org.springframework.boot.web.servlet.ServletListenerRegistrationBean
Spring Boot  1.4.0 之前
org.springframework.boot.context.embedded.ServletListenerRegistrationBean
3.暴露 Spring Bean
@Bean

MyServlet2 

public class MyServlet2 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Writer writer = resp.getWriter();
        //是通過super.init(servletConfig)初始化好纔可以得到ServletContent
        ServletContext context = getServletContext();
        context.log("myServlet do get 2");

        writer.write("<html><body>Hello,World“”“ from myservlet2</body></html>");
    }
}
MyFilter2 

public class MyFilter2 extends OncePerRequestFilter {

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        doSomething();
        filterChain.doFilter(request,response);
    }

    public void doSomething() {

        RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
        ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes) requestAttributes;
        HttpServletRequest request = servletRequestAttributes.getRequest();
        
        ServletContext servletContext = request.getServletContext();
        String requestURI = request.getRequestURI();
        servletContext.log(requestURI + " was filtered!");
    }
}


SpringBootLearnApplication 

@SpringBootApplication
@ServletComponentScan(basePackages = {"com.yun.springbootlearn.servlet"})
public class SpringBootLearnApplication extends SpringBootServletInitializer {

	public static void main(String[] args) {
		SpringApplication.run(SpringBootLearnApplication.class, args);
		System.out.println("start");
	}

	@Bean
	public static ServletRegistrationBean servletRegistrationBean(){
		ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean();

		servletRegistrationBean.setServlet(new MyServlet2());
		servletRegistrationBean.setName("my-servlet2");
		servletRegistrationBean.addUrlMappings("/spring-boot/myservlet2");
		servletRegistrationBean.addInitParameter("myname","myvalue");
		return servletRegistrationBean;
	}

	@Bean
	public static FilterRegistrationBean filterRegistrationBean(){
		FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
		filterRegistrationBean.setFilter(new MyFilter2());
		filterRegistrationBean.addServletNames("my-servlet2");
		filterRegistrationBean.setDispatcherTypes(DispatcherType.REQUEST,DispatcherType.FORWARD,DispatcherType.INCLUDE);
		return filterRegistrationBean;
	}

	@Bean
	public static ServletListenerRegistrationBean servletListenerRegistrationBean() {
		ServletListenerRegistrationBean servletListenerRegistrationBean = new ServletListenerRegistrationBean();
		servletListenerRegistrationBean.setListener(new MyServletRequestListener());
		return servletListenerRegistrationBean;
	}
}

激活 傳統Servlet Web部署

1.需要引入相應的依賴
		<!-- JSP 渲染引擎 -->
		<dependency>
			<groupId>org.apache.tomcat.embed</groupId>
			<artifactId>tomcat-embed-jasper</artifactId>
		</dependency>

		<!-- JSTL -->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>jstl</artifactId>
		</dependency>
		
2.修改打包方式爲war包
	<packaging>war</packaging>


3.Spring Boot 1.4.0 開始 繼承
org.springframework.boot.web.support.SpringBootServletInitializer

@SpringBootApplication
@ServletComponentScan(basePackages = {"com.yun.springbootlearn.servlet"})
public class SpringBootLearnApplication extends SpringBootServletInitializer {

}

4.組裝 org.springframework.boot.builder.SpringApplicationBuilder

protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
		builder.sources(SpringBootLearnApplication.class);
		return builder;
	}

5.配置JSP視圖 在application.properties
org.springframework.boot.autoconfigure.web.WebMvcProperties
spring.mvc.view.prefix=/WEB-INF/
spring.mvc.view.suffix=.jsp