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  • Servlet表单Get和Post读取

    新建一个maven的war工程，如果没有web.xml新增一个web.xml或者拷贝一个例如：

    <?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_2_5.xsd" 
         version="2.5">

</web-app>

    工程代码结构如图所示：

    pom.xml添加相关依赖:

    <project xmlns="http://maven.apache.org/POM/4.0.0" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>servlet</groupId>
  <artifactId>servlet</artifactId>
  <version>1.0.0</version>
  <packaging>war</packaging>
  
  <dependencies>
    <dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.1.0</version>
      </dependency>
  </dependencies>
</project>

    一、HelloWorld入门示例

    java代码如下：

    package servlet.enter;

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 ServletEnter extends HttpServlet{

    private static final long serialVersionUID = -876565140384532446L;
    
    private String message;
    
    public void init() throws ServletException{        
        message="HelloWorld!";        
    }
    
    public void doGet(HttpServletRequest request,HttpServletResponse response)
        throws ServletException,IOException{
        response.setContentType("text/html");
        
        PrintWriter out=response.getWriter();
        out.println("<h1>"+message+"</h1>");
    }
    
    public void destroy(){
        
    }
}

    web.xml配置如下：

      <servlet>
    <servlet-name>ServletEnter</servlet-name>
    <servlet-class>servlet.enter.ServletEnter</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ServletEnter</servlet-name>
    <url-pattern>/ServletEnter</url-pattern>
  </servlet-mapping>

    若是报以下错误，多半是Servlet-class的路径没有配对。重新修改下即可。

    二、Get方式获取表单数据

    java代码如下：

    package servlet.form;

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;

@WebServlet("/GetFormServlet")
public class GetFormServlet extends HttpServlet {
    
    private static final long serialVersionUID = 1L;
    
    public GetFormServlet() {    
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        
        PrintWriter out=response.getWriter();
        String title="使用Get方法读取表单信息";
        String name= new String(request.getParameter("name").getBytes("ISO8859-1"),"UTF-8");
        String docType="<!DOCTYPE html> 
";
        out.println(docType+
                "<html>
" +
                "<head><title>" + title + "</title></head>
" +
                "<body bgcolor="#f0f0f0">
" +
                "<h1 align="center">" + title + "</h1>
" +
                "<ul>
" +
                "  <li><b>站点名</b>："
                + name + "
" +
                "  <li><b>网址</b>："
                + request.getParameter("url") + "
" +
                "</ul>
" +
                "</body></html>");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}
    可以通过 @WebServlet("/GetFormServlet")来配置Servlet路径，这样就不要在web.xml里头配置Servlet了。
    Servlet通过request.getParameter来获取参数，当参数为中文的时候，要注意乱码处理
     String name= new String(request.getParameter("name").getBytes("ISO8859-1"),"UTF-8");
    Servlet 处理表单数据，这些数据会根据不同的情况使用不同的方法自动解析：
    getParameter()：您可以调用 request.getParameter() 方法来获取表单参数的值。
getParameterValues()：如果参数出现一次以上，则调用该方法，并返回多个值，例如复选框。
getParameterNames()：如果您想要得到当前请求中的所有参数的完整列表，则调用该方法。
    地址栏输入：
    http://localhost:8081/servlet/GetFormServlet?name=shawWey&url=www.shawwey.com

      浏览器效果如图：

    三、Post方式获取表单数据

    java 代码如下：

    package servlet.form;

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;

    @WebServlet("/PostFormServlet")
    public class PostFormServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public PostFormServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out=response.getWriter();
        String title="使用Post方法读取表单信息";
        String name= new String(request.getParameter("name").getBytes("ISO8859-1"),"UTF-8");
        String docType="<!DOCTYPE html> 
";
        out.println(docType+
                "<html>
" +
                "<head><title>" + title + "</title></head>
" +
                "<body bgcolor="#f0f0f0">
" +
                "<h1 align="center">" + title + "</h1>
" +
                "<ul>
" +
                "  <li><b>站点名</b>："
                + name + "
" +
                "  <li><b>网址</b>："
                + request.getParameter("url") + "
" +
                "</ul>
" +
                "</body></html>");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

    页面html代码如下：

    <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>测试教程</title>
</head>
<body>
<form action="PostFormServlet" method="GET">
网址名：<input type="text" name="name">
<br />
网址：<input type="text" name="url" />
<input type="submit" value="提交" />
</form>
</body>
</html>

    浏览器效果：

           

     四、另一个表单实例

    java代码如下：

    package servlet.form;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Form extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    public Form() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 设置响应内容类型
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        String title = "读取所有的表单数据";
        String docType =
            "<!doctype html public "-//w3c//dtd html 4.0 " +
            "transitional//en">
";
            out.println(docType +
            "<html>
" +
            "<head><meta charset="utf-8"><title>" + title + "</title></head>
" +
            "<body bgcolor="#f0f0f0">
" +
            "<h1 align="center">" + title + "</h1>
" +
            "<table width="100%" border="1" align="center">
" +
            "<tr bgcolor="#949494">
" +
            "<th>参数名称</th><th>参数值</th>
"+
            "</tr>
");

        Enumeration paramNames = request.getParameterNames();

        while(paramNames.hasMoreElements()) {
            String paramName = (String)paramNames.nextElement();
            out.print("<tr><td>" + paramName + "</td>
");
            String[] paramValues =
            request.getParameterValues(paramName);
            // 读取单个值的数据
            if (paramValues.length == 1) {
                String paramValue = paramValues[0];
                if (paramValue.length() == 0)
                    out.println("<td><i>没有值</i></td>");
                else
                    out.println("<td>" + paramValue + "</td>");
            } else {
                // 读取多个值的数据
                out.println("<td><ul>");
                for(int i=0; i < paramValues.length; i++) {
                out.println("<li>" + paramValues[i]);
            }
                out.println("</ul></td>");
            }
            out.print("</tr>");
        }
        out.println("
</table>
</body></html>");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

    配置web.xml

      <servlet>
    <description></description>
    <display-name>Form</display-name>
    <servlet-name>Form</servlet-name>
    <servlet-class>servlet.form.Form</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Form</servlet-name>
    <url-pattern>/Form</url-pattern>
  </servlet-mapping>

    html页面代码如下：

    <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<form action="Form" method="POST" target="_blank">
<input type="checkbox" name="maths" checked="checked" /> 数学
<input type="checkbox" name="physics"  /> 物理
<input type="checkbox" name="chemistry" checked="checked" /> 化学
<input type="submit" value="选择学科" />
</form>

</body>
</html>

     本文代码示例： 代码下载
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  • 原文地址：https://www.cnblogs.com/shawWey/p/8126492.html
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