Servlet学习（四）：urlPattern配置与XML配置

1、urlPattern配置

Servlet类编写好后，要想被访问到，就需要配置其访问路径（urlPattern）

• 一个Servlet,可以配置多个urlPattern

  package com.itheima.web;
  
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.annotation.WebServlet;
  
  /**
  * urlPattern: 一个Servlet可以配置多个访问路径
  */
  @WebServlet(urlPatterns = {"/demo1","/demo2"})
  public class ServletDemo7 extends MyHttpServlet {
  
      @Override
      protected void doGet(ServletRequest req, ServletResponse res) {
          
          System.out.println("demo1 get...");
      }
      @Override
      protected void doPost(ServletRequest req, ServletResponse res) {
      }
  }
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• urlPattern配置规则

  • 精确匹配

    

    /**
     * UrlPattern:
     * * 精确匹配
     */
    @WebServlet(urlPatterns = "/user/select")
    public class ServletDemo8 extends MyHttpServlet {
    
        @Override
        protected void doGet(ServletRequest req, ServletResponse res) {
    
            System.out.println("demo8 get...");
        }
        @Override
        protected void doPost(ServletRequest req, ServletResponse res) {
        }
    }
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  • 目录匹配

    

    package com.itheima.web;
    
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.annotation.WebServlet;
    
    /**
     * UrlPattern:
     * * 目录匹配: /user/*
     */
    @WebServlet(urlPatterns = "/user/*")
    public class ServletDemo9 extends MyHttpServlet {
    
        @Override
        protected void doGet(ServletRequest req, ServletResponse res) {
    
            System.out.println("demo9 get...");
        }
        @Override
        protected void doPost(ServletRequest req, ServletResponse res) {
        }
    }
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  • 扩展名匹配

    

    package com.itheima.web;
    
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.annotation.WebServlet;
    
    /**
     * UrlPattern:
     * * 扩展名匹配: *.do
     */
    @WebServlet(urlPatterns = "*.do")
    public class ServletDemo10 extends MyHttpServlet {
    
        @Override
        protected void doGet(ServletRequest req, ServletResponse res) {
    
            System.out.println("demo10 get...");
        }
        @Override
        protected void doPost(ServletRequest req, ServletResponse res) {
        }
    }
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    访问路径http://localhost:8080/web-demo/任意.do

    注意:

    1. 如果路径配置的不是扩展名，那么在路径的前面就必须要加/否则会报错
    2. 如果路径配置的是*.do,那么在*.do的前面不能加/,否则会报错

  • 任意匹配

    

    package com.itheima.web;
    
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.annotation.WebServlet;
    
    /**
     * UrlPattern:
     * * 任意匹配： /
     */
    @WebServlet(urlPatterns = "/")
    public class ServletDemo11 extends MyHttpServlet {
    
        @Override
        protected void doGet(ServletRequest req, ServletResponse res) {
    
            System.out.println("demo11 get...");
        }
        @Override
        protected void doPost(ServletRequest req, ServletResponse res) {
        }
    }
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    package com.itheima.web;
    
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.annotation.WebServlet;
    
    /**
     * UrlPattern:
     * * 任意匹配： /*
     */
    @WebServlet(urlPatterns = "/*")
    public class ServletDemo12 extends MyHttpServlet {
    
        @Override
        protected void doGet(ServletRequest req, ServletResponse res) {
    
            System.out.println("demo12 get...");
        }
        @Override
        protected void doPost(ServletRequest req, ServletResponse res) {
        }
    }
    
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    注意:/和/*的区别?

    1. 当我们的项目中的Servlet配置了 “/”,会覆盖掉tomcat中的DefaultServlet,当其他的url-pattern都匹配不上时都会走这个Servlet

    2. 当我们的项目中配置了"/*",意味着匹配任意访问路径

    3. DefaultServlet是用来处理静态资源，如果配置了"/"会把默认的覆盖掉，就会引发请求静态资源的时候没有走默认的而是走了自定义的Servlet类，最终导致静态资源不能被访问

  • 五种配置的优先级为 精确匹配 > 目录匹配 > 扩展名匹配 > /* > /

2、XML配置

前面对应Servlet的配置，我们都使用的是@WebServlet,这个是Servlet从3.0版本后开始支持注解配置，3.0版本前只支持XML配置文件的配置方法。

对于XML的配置步骤有两步:

• 编写Servlet类

package com.itheima.web;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebServlet;

public class ServletDemo13 extends MyHttpServlet {

    @Override
    protected void doGet(ServletRequest req, ServletResponse res) {

        System.out.println("demo13 get...");
    }
    @Override
    protected void doPost(ServletRequest req, ServletResponse res) {
    }
}
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• 在web.xml中配置该Servlet

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    
    
    
    
    <servlet>
        
        <servlet-name>demo13servlet-name>
        
        <servlet-class>com.itheima.web.ServletDemo13servlet-class>
    servlet>

    
    <servlet-mapping>
        
        <servlet-name>demo13servlet-name>
        
        <url-pattern>/demo13url-pattern>
    servlet-mapping>
web-app>
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