1.页面的数据表单
在使用Servlet处理用户请求之前，先准备一个页面，该页面用来提供数据表单。数据表单就是HTML中的<form>...</form>部分，当用户单击Submit按钮提交表单之后，表单中包含的一些变量（或者成为字段）将会被发送到服务器端进行处理。下面编写一个HTML文件，文件代码如下：
add.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>add.html</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=GB2312"> <!--<link rel="stylesheet" type="text/css" href="./styles.css">--> </head> <body>
<form action="/jdbc_servlet/servlet/addServlet" method="post">
<label>请输入部门信息：</label><br><br>
<label>部门号：</label><br>
<input type="text" name="id"/><br>
<label>部门名：</label><br>
<input type="text" name="name"/><br>
<label>部门人数：</label><br>
<input type="text" name="num"/><br>
<label>地址：</label><br>
<input type="text" name="address"/><br><br>
<input type="submit" value="提交"/><br>
</form>
</body>
</html>
2.添加数据
Servlet的好处之一就是可以简单地获得表单中的数据。在Servlet中使用JDBC技术实现添加的代码如下：
addServlet.java
package com.cn.add; import java.io.IOException;
import java.io.PrintWriter;
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 addServlet extends HttpServlet { /**
* Constructor of the object.
*/
public addServlet() {
super();
} /**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
} /**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setContentType("text/html;charset=gb2312");
PrintWriter out = response.getWriter();
this.doPost(request, response);
out.flush();
out.close();
} /**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("到了Servlet！！！");
response.setContentType("text/html;charset=gb2312");
request.setCharacterEncoding("gb2312");
PrintWriter out = response.getWriter();
String id = request.getParameter("id"); //获取部门编号
String name = request.getParameter("name"); //获取部门名称
String address = request.getParameter("address"); //获取部门所在地址
int num = Integer.parseInt(request.getParameter("num")); //获取部门人数
Connection conn = null; //声明一个Connection对象，用来连接数据库
PreparedStatement pstmt = null; //声明PreparedStatement对象，用来向数据库插入数据条数据
try {
//连接到MySQL数据库中的bank数据库模式
Class.forName("com.mysql.jdbc.Driver");
System.out.println("创建驱动成功！");
//连接数据库
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/bank", "root", "1234");
System.out.println("连接数据库成功！");
//插入数据的SQL语句
String sql = "INSERT INTO dept(id,d_name,address,empnumber) VALUES(?,?,?,?)";
pstmt = conn.prepareStatement(sql);
//设置插入数据的顺序
pstmt.setString(1, id);
pstmt.setString(2, name);
pstmt.setString(3, address);
pstmt.setInt(4, num);
int result = pstmt.executeUpdate();
//判断执行结果
if (result == 1) {
out.print("插入数据成功！");
}else {
out.print("插入数据失败！请重新插入！");
}
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
out.flush();
out.close();
} /**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
} }
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>addServlet</servlet-name>
<servlet-class>com.cn.add.addServlet</servlet-class>
</servlet> <servlet-mapping>
<servlet-name>addServlet</servlet-name>
<url-pattern>/servlet/addServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
文件整体框架如下：
3.查看单条数据
一般一条数据的id是唯一的，查看单条记录的时候，可以根据id来查询。HTML页面的代码如下：
showById.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>showById.html</title> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=gb2312"> <!--<link rel="stylesheet" type="text/css" href="./styles.css">--> </head> <body>
<form name="f1" id="f1" action="/jdbc_servlet/servlet/SearchEmployee" method="post">
<table border="0">
<tr>
<td>请输入部门编号：</td><tr/><tr/>
<td><input type="text" name="id"></td>
</tr>
<tr>
<td colspan="2" align="left"><input type="submit" value="查找"></td>
</tr>
</table>
</form>
</body>
</html>
在该页面中输如id号，点击查找按钮时会进入查询的Servlet，在Servlet中处理根据id查询的操作。根据id查询的Servlet代码如下：
SearchEmployee.java
package com.cn.query; import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
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 SearchEmployee extends HttpServlet { /**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
} /**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setContentType("text/html;charset=gb2312");
request.setCharacterEncoding("gb2312");
PrintWriter out = response.getWriter();
String id = request.getParameter("id"); //获取部门编号
Connection conn = null; //声明一个Connection对象，用来连接数据库
PreparedStatement pstmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("创建驱动成功！");
//连接数据库
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/bank", "root", "1234");
System.out.println("连接数据库成功！");
String sql = "SELECT * FROM dept WHERE id = ?";
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, id);
rs = pstmt.executeQuery();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
while(rs.next()){
out.print("部门编号："+rs.getString(1)+"\n");
out.print("部门名称："+rs.getString(2)+"\n");
out.print("部门地址："+rs.getString(3)+"\n");
out.print("部门人数："+rs.getString(4)+"\n");
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
out.flush();
out.close();
} /**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setContentType("text/html;charset=gb2312");
request.setCharacterEncoding("gb2312");
PrintWriter out = response.getWriter();
this.doGet(request, response);
out.flush();
out.close();
} /**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
} }
目录结构如下：
4.显示一张表中的全部数据
显示表中全部数据信息的Servlet代码如下：
DeptList.java
package com.cn.query; import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; public class DeptList extends HttpServlet { /**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setContentType("text/html;charset=gb2312");
request.setCharacterEncoding("gb2312");
PrintWriter out = response.getWriter();
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/bank", "root", "1234");
stmt = conn.createStatement();
rs = stmt.executeQuery("SELECT * FROM dept");
//在页面中显示表中的所有信息
out.println(
"<html>"+
"<head><title>部门表信息</title></head>"+
"<body>");
out.println("<h1>部门表信息:</h1><br><br>");
//循环遍历输出查询结果
while(rs.next()){
out.print("部门编号：");
out.print(rs.getString(1)+"\t");
out.print("部门名称：");
out.print(rs.getString(2)+"\t");
out.print("部门地址：");
out.print(rs.getString(3)+"\t");
out.print("部门人数：");
out.print(rs.getString(4)+"\t");
out.print("<br>");
}
out.print("</body></html>");
out.close();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} public void init() throws ServletException {
// Put your code here
} }