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.Java
package 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
public 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);
}
}
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MyServlet.java
package 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>");
}
}
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使用注解注册Servlet示例代码
SpringBootSampleApplication.java
package 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
@ServletComponentScan
public class SpringBootSampleApplication {
public static void main(String[] args) {
SpringApplication.run(SpringBootSampleApplication.class, args);
}
}
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MyServlet2.java
package 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.MyServlet2
public 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>");
}
}
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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;
}
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当然,这里可以对DispatcherServlet做很多修改,并非只是UrlMappings。
http://blog.csdn.net/catoop/article/details/50501686