关于Web中资源跳转的问题：
转发和重定向基本代码：
package com.bjpowernode.javaweb; import java.io.IOException; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class AServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//向request范围中存储数据
request.setAttribute("username", "zhangsan"); //转发forward：一次请求
//request.getRequestDispatcher("/b").forward(request, response); //重定向redirect：两次请求
//执行到此处之后，将/prj-servlet-16/b路径响应给浏览器，浏览器又向服务器发送了一次全新的请求
response.sendRedirect("/prj-servlet-16/b");
//response.sendRedirect(request.getContextPath() + "/b");
}
}
package com.bjpowernode.javaweb; import java.io.IOException; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class BServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//向request范围中取数据
Object obj = request.getAttribute("username");
System.out.println(obj);
}
}
使用重定向解决页面刷新问题：
<html>
<head>
<title>save user</title>
<meta charset="UTF-8">
</head>
<body>
<form action="/prj-servlet-17/save" method="post">
usercode<input type="text" name="usercode">
username<input type="text" name="username">
<input type="submit" value="save">
</form>
</body>
</html>
package com.bjpowernode.javaweb.servlet; import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class SaveUserServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//解决中文乱码
request.setCharacterEncoding("UTF-8"); //获取表单提供的数据
String usercode = request.getParameter("usercode");
String username = request.getParameter("username"); //JDBC
Connection conn = null;
PreparedStatement ps = null;
int count = 0;
try{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test1", "root", "248xiaohai");
conn.setAutoCommit(false);
String sql = "insert into t_user(usercode,username) values(?,?)";
ps = conn.prepareStatement(sql);
ps.setString(1, usercode);
ps.setString(2, username);
count = ps.executeUpdate();
conn.commit();
} catch (Exception e) {
e.printStackTrace();
} finally {
if(ps != null){
try {
ps.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(conn != null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
} if(count == 1){
//保存成功，跳转到成功页面
//转发,刷新的时候会重复保存数据,因为刷新的是第一个请求/prj-servlet-17/save
//request.getRequestDispatcher("/success.html").forward(request, response);
//重定向,刷新的时候不会重复保存数据,因为刷新的是后一个请求/prj-servlet-17/success.html
response.sendRedirect(request.getContextPath() + "/success.html");
}
}
} }