Spring Boot Servlet
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来源:http://blog.csdn.net/catoop/article/details/50501686
上一篇我们对如何创建Controller 来响应JSON 以及如何显示数据到页面中,已经有了初步的了解。 Web开发使用 Controller 基本上可以完成大部分需求,但是我们还可能会用到 Servlet、Filter、Listener、Interceptor 等等。当使用Spring-Boot时,嵌入式Servlet容器通过扫描注解的方式注册Servlet、Filter和Servlet规范的所有监听器(如HttpSessionListener监听器)。 Spring boot 的主 Servlet 为 DispatcherServlet,其默认的url-pattern为“/”。也许我们在应用中还需要定义更多的Servlet,该如何使用SpringBoot来完成呢?在spring boot中添加自己的Servlet有两种方法,代码注册Servlet和注解自动注册(Filter和Listener也是如此)。 一、代码注册通过ServletRegistrationBean、 FilterRegistrationBean 和 ServletListenerRegistrationBean 获得控制。 也可以通过实现 ServletContextInitializer 接口直接注册。二、在 SpringBootApplication 上使用@ServletComponentScan 注解后,Servlet、Filter、Listener 可以直接通过 @WebServlet、@WebFilter、@WebListener 注解自动注册,无需其他代码。通过代码注册Servlet示例代码:SpringBootSampleApplication.javapackage org.springboot.sample;import org.springboot.sample.servlet.MyServlet;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.context.embedded.ServletRegistrationBean;import org.springframework.boot.web.servlet.ServletComponentScan;import org.springframework.context.annotation.Bean;import org.springframework.web.servlet.DispatcherServlet;@SpringBootApplicationpublic class SpringBootSampleApplication { /** * 使用代码注册Servlet(不需要@ServletComponentScan注解) * * @return * @author SHANHY * @create 2016年1月6日 */ @Bean public ServletRegistrationBean servletRegistrationBean() { return new ServletRegistrationBean(new MyServlet(), "/xs/*");// ServletName默认值为首字母小写,即myServlet } public static void main(String[] args) { SpringApplication.run(SpringBootSampleApplication.class, args); }}MyServlet.javapackage org.springboot.sample.servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet * * @author 单红宇(365384722) * @myblog http://blog.csdn.net/catoop/ * @create 2016年1月6日 *///@WebServlet(urlPatterns="/xs/*", description="Servlet的说明")public class MyServlet extends HttpServlet{ private static final long serialVersionUID = -8685285401859800066L; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println(">>>>>>>>>>doGet()<<<<<<<<<<<"); doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println(">>>>>>>>>>doPost()<<<<<<<<<<<"); resp.setContentType("text/html"); PrintWriter out = resp.getWriter(); out.println("<html>"); out.println("<head>"); out.println("<title>Hello World</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>大家好,我的名字叫Servlet</h1>"); out.println("</body>"); out.println("</html>"); }}使用注解注册Servlet示例代码SpringBootSampleApplication.javapackage org.springboot.sample;import org.springboot.sample.servlet.MyServlet;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.context.embedded.ServletRegistrationBean;import org.springframework.boot.web.servlet.ServletComponentScan;import org.springframework.context.annotation.Bean;import org.springframework.web.servlet.DispatcherServlet;@SpringBootApplication@ServletComponentScanpublic class SpringBootSampleApplication { public static void main(String[] args) { SpringApplication.run(SpringBootSampleApplication.class, args); }}MyServlet2.javapackage org.springboot.sample.servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet * * @author 单红宇(365384722) * @myblog http://blog.csdn.net/catoop/ * @create 2016年1月6日 */@WebServlet(urlPatterns="/xs/myservlet", description="Servlet的说明") // 不指定name的情况下,name默认值为类全路径,即org.springboot.sample.servlet.MyServlet2public class MyServlet2 extends HttpServlet{ private static final long serialVersionUID = -8685285401859800066L; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println(">>>>>>>>>>doGet2()<<<<<<<<<<<"); doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println(">>>>>>>>>>doPost2()<<<<<<<<<<<"); resp.setContentType("text/html"); PrintWriter out = resp.getWriter(); out.println("<html>"); out.println("<head>"); out.println("<title>Hello World</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>大家好,我的名字叫Servlet2</h1>"); out.println("</body>"); out.println("</html>"); }}使用 @WebServlet 注解,其中可以设置一些属性。有个问题:DispatcherServlet 默认拦截“/”,MyServlet 拦截“/xs/*”,MyServlet2 拦截“/xs/myservlet”,那么在我们访问 http://localhost:8080/xs/myservlet 的时候系统会怎么处理呢?如果访问 http://localhost:8080/xs/abc 的时候又是什么结果呢?这里就不给大家卖关子了,其结果是“匹配的优先级是从精确到模糊,复合条件的Servlet并不会都执行”既然系统DispatcherServlet 默认拦截“/”,那么我们是否能做修改呢,答案是肯定的,我们在SpringBootSampleApplication中添加代码: /** * 修改DispatcherServlet默认配置 * * @param dispatcherServlet * @return * @author SHANHY * @create 2016年1月6日 */ @Bean public ServletRegistrationBean dispatcherRegistration(DispatcherServlet dispatcherServlet) { ServletRegistrationBean registration = new ServletRegistrationBean(dispatcherServlet); registration.getUrlMappings().clear(); registration.addUrlMappings("*.do"); registration.addUrlMappings("*.json"); return registration; }当然,这里可以对DispatcherServlet做很多修改,并非只是UrlMappings。
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