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[Java教程]HTML调用servlet(一)


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

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<!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>
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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

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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  }}
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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

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<!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>
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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

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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  }}
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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

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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  }}