Servlet中的service方法

绝地灬酷狼 2022-06-08 09:24 164阅读 0赞

Servlet中的service方法用于应答浏览器请求，每次请求都会调用该方法。

@Override public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } }

ServletRequest:封装了请求信息，可以从中获取到任何的请求信息。

ServletResponse：封装了响应信息，用于响应用户请求。

这两个接口都是服务器给予实现的，并在服务器调用service方法时传入。

1.ServletRequest：

1.1  获取请求参数：

1.1.1  String getParameter(String name); 根据名字获取值

html:

xml:

<servlet>
      
        <servlet-name>loginServlet</servlet-name>
        
        <servlet-class>com.sa.servlet.LoginServlet</servlet-class>
      </servlet>
      
      <servlet-mapping>
      
        <servlet-name>loginServlet</servlet-name>
        
        <url-pattern>/login</url-pattern>
      </servlet-mapping>

LoginServlet:

@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
            String login=request.getParameter("login");
            String password=request.getParameter("password");
            System.out.println("login:"+login);
            System.out.println("password:"+password);
    
    	}

输出结果:

1.1.2  Map<String, String>  getParameterMap();返回请求参数的键值对。

key:参数名,value:参数值，String\[\] 类型

@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		Map<String, String[]> map=request.getParameterMap();
    		for (String key : map.keySet()) {
    			   System.out.println("key= "+ key + " and value= " + Arrays.toString(map.get(key)));
    			  }
    
    	}

输出结果:

key= login and value= [admin]
    key= password and value= [123]
    key= interesting and value= [Party, Shopping]

1.1.3  Enumeration<String>  getParameterNames();返回参数名对应的Enumeration对象。

@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		//Map<String, String> request.getParameterMap();
    		//Enumeration<String> request.getParameterNames();
    		//String[] request.getParameterValues(arg0);
    		Enumeration<String> enums=request.getParameterNames();
    		while(enums.hasMoreElements()){
    			String name=enums.nextElement();
    			String[] value=request.getParameterValues(name);
    			System.out.println("name:"+name+",value:"+Arrays.toString(value));
    		}

查看结果：

name:login,value:[admin]
    name:password,value:[123]
    name:interesting,value:[Playing, Party]

1.1.4  String\[\] getParameterValues(String name);根据名字获取值数组，例如checkbox

html：

<!DOCTYPE html>
    <html>
      <head>
        <title>login.html</title>
    	
        <meta name="keywords" content="keyword1,keyword2,keyword3">
        <meta name="description" content="this is my page">
        <meta name="content-type" content="text/html; charset=UTF-8">
        
        
    
      </head>
      
      <body>
        <form name="f1" id="f1" action="login" method="post">
          <table>
            <tr>
              <td>Login:</td>
              <td><input type="text" name="login" id="login"></td>
            </tr>
            <tr>
              <td>Password:</td>
              <td><input type="password" name="password" id="password"></td>
            </tr> 
            <tr>
              <td>interesting:</td>
              <td>
              <input type="checkbox" name="interesting" value="Playing"/>Playing
              <input type="checkbox" name="interesting" value="TV"/>TV
              <input type="checkbox" name="interesting" value="Party"/>Party
              <input type="checkbox" name="interesting" value="Sport"/>Sport
              <input type="checkbox" name="interesting" value="Shopping"/>Shopping
              </td>
            </tr>
            <tr>
              <td colspan="2"><input type="submit"></td>
            </tr>
    
          </table>
        </form>
      </body>
    </html>

LoginServlet：

@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
            String login=request.getParameter("login");
            String password=request.getParameter("password");
            String[] interesting=request.getParameterValues("interesting");
            System.out.println("login:"+login);
            System.out.println("password:"+password);
            System.out.println("interesting:"+Arrays.toString(interesting));
    
    	}

输出结果：

![Center][]  
  
  1.2   获取请求的URI：

HttpServletRequest是ServletRequest的子接口，针对于HTTP请求所定义，里面有

大量获取HTTP信息的方法。

@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		HttpServletRequest httpServletRequest=(HttpServletRequest) request;
    		String uri=httpServletRequest.getRequestURI();
    		System.out.println("uri:"+uri);
    
    	}

输出结果：

uri:/MyLab2/login

1.3   获取请求方式：

@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		HttpServletRequest httpServletRequest=(HttpServletRequest) request;
    		String method=httpServletRequest.getMethod();
    		System.out.println("method:"+method);
    
    	}

输出结果：

method:POST

2. ServletReponse：

2.1   getWriter（）：

返回PrintWriter对象，调用该对象的print()方法，把print()中参数打印在网页上。

@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
            PrintWriter writer=response.getWriter();
            writer.println("hello world");
    
    	}

查看页面：

![Center 1][]  
  2.2  setContentType（）：

@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		response.setContentType("application/msword");
            PrintWriter writer=response.getWriter();
            writer.println("hello world");
    
    	}

设置为内容类型为“application/msword”，这样返回的内容下载下来：

![Center 2][]  
  
      2.3 void sendRedirect（String location）：

请求的重定向。（此方法为HttpServletResponse中定义）

在web.xml文件中设置两个WEB应用的初始化参数：user,password.

定义一个login.html,里边定义两个请求字段：user,password,发送请求到loginServlet.

在loginServlet中，获取请求的user,password,比较其和web.xml文件中的初始化参数是否一致，

若一致，则响应: hello,xxx；若不一致，则响应: sorry ,xxx;

html:

web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="http://java.sun.com/xml/ns/javaee" 
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
        
      <context-param>
          <param-name>user</param-name>
          <param-value>sasa</param-value>
       </context-param>
          <context-param>
          <param-name>password</param-name>
          <param-value>123</param-value>
       </context-param> 
      
      <servlet>
      
        <servlet-name>loginServlet</servlet-name>
        
        <servlet-class>com.sa.servlet.LoginServlet</servlet-class>
      </servlet>
      
      <servlet-mapping>
      
        <servlet-name>loginServlet</servlet-name>
        
        <url-pattern>/login</url-pattern>
      </servlet-mapping> 
     
    </web-app>

LoginServlet:

package com.sa.servlet;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.PrintWriter;
    import java.util.Arrays;
    import java.util.Enumeration;
    import java.util.Map;
    
    import javax.servlet.Servlet;
    import javax.servlet.ServletConfig;
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class LoginServlet implements Servlet {
         
    	public LoginServlet(){
    
    	}
    	@Override
    	public void destroy() {
    		// TODO Auto-generated method stub
    
    	}
    
    	@Override
    	public ServletConfig getServletConfig() {
    		// TODO Auto-generated method stub
    
    		return null;
    	}
    
    	@Override
    	public String getServletInfo() {
    		// TODO Auto-generated method stub
    
    		return null;
    	}
    
    	@Override
    	public void init(ServletConfig arg0) throws ServletException {
    		// TODO Auto-generated method stub
    
    	}
    
    	@Override
    	public void service(ServletRequest request, ServletResponse response)
    			throws ServletException, IOException {
    		// TODO Auto-generated method stub
            String user=request.getParameter("login");
            String password=request.getParameter("password");
            ServletContext servletContext=request.getServletContext();
            String user2=servletContext.getInitParameter("user");
            String password2=servletContext.getInitParameter("password");
            //HttpServletResponse httpServletResponse=(HttpServletResponse) response;
            PrintWriter writer=response.getWriter();
            if(user.equals(user2)&&password.equals(password2)){       	       	
            	writer.println("hello,"+user);
            }else{
            	writer.println("sorry,"+user);
            }
    
    	}
    	
    
    }

测试:

![Center 3][]

![Center 4][]

![Center 5][]

![Center 6][]

[Center]: /images/20220608/865fe598ce5b4b5892725cc72156902f.png
[Center 1]: /images/20220608/fc5913d9d7404b278a4ef2f810ce57b3.png
[Center 2]: /images/20220608/8a9ecbf425824997bad8fa606a83da56.png
[Center 3]: /images/20220608/e4d7576d42a94b198960a168564031c2.png
[Center 4]: /images/20220608/729b8426d1144c34be3c0c7358b4de54.png
[Center 5]: /images/20220608/dd9c97c53260427094d1f1a3a97c612f.png
[Center 6]: /images/20220608/4dea8568d7d54dd4a1a0edbc0d86c8ab.png