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。
1.通过代码注册Servlet示例代码
1).SpringBootSimpleApplication.Java类:
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package com.example;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import com.example.servlet.MyServlet;
@SpringBootApplication
public class SpringBootSimpleApplication {
/**
* 使用代码注册Servlet(不需要@ServletComponentScan注解)
*/
@Bean
public ServletRegistrationBean servletRegistrationBean() {
return new ServletRegistrationBean( new MyServlet(), "/st/*" ); // ServletName默认值为首字母小写,即myServlet
}
public static void main(String[] args) {
SpringApplication.run(SpringBootSimpleApplication. class , args);
}
}
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2).MyServlet.java类:
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package com.example.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class MyServlet extends HttpServlet{
@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" );
resp.setCharacterEncoding( "utf-8" );
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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2.使用注解注册Servlet示例代码
1).SpringBootSimpleApplication.java类:
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package com.example;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import com.example.servlet.MyServlet;
@SpringBootApplication
@ServletComponentScan
public class SpringBootSimpleApplication {
/**
* 使用代码注册Servlet(不需要@ServletComponentScan注解)
*/
@Bean
public ServletRegistrationBean servletRegistrationBean() {
return new ServletRegistrationBean( new MyServlet(), "/st/*" ); // ServletName默认值为首字母小写,即myServlet
}
public static void main(String[] args) {
SpringApplication.run(SpringBootSimpleApplication. class , args);
}
}
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2).MyServlet2.java类:
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package com.example.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;
// 不指定name的情况下,name默认值为类全路径,即com.example.servlet.MyServlet2
@WebServlet (urlPatterns= "/st/myservlet2" , description= "Servlet的说明" )
public class Myservlet2 extends HttpServlet{
@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" );
resp.setCharacterEncoding( "utf-8" );
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。
3.访问结果
4.DispatcherServlet默认拦截
DispatcherServlet 默认拦截“/”,MyServlet 拦截“/st/*”,MyServlet2 拦截“/st/myservlet”,那么在我们访问 http://localhost:8080/st/myservlet2 的时候系统会怎么处理呢?如果访问 http://localhost:8080/st/abc的时候又是什么结果呢?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:
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/**
* 修改DispatcherServlet默认配置
*/
@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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可以通过注入DispatcherServlet 然后用ServletRegistrationBean包裹一层 动态的加上一些初始参数。
原文链接:http://www.cnblogs.com/web424/p/6755950.html