JavaWeb程序利用Servlet的对SQLserver增删改查操作

声明:学了几天终于将增删改查的操作掌握了，也发现了一些问题，所以总结一下.

重点:操作数据库主要用的是SQL语句跟其他无关.

一:前提知识:PreparedStatement

PreperedStatement是Statement的子类，它的实例对象可以通过调用Connection.preparedStatement()方法获得，相对于Statement对象而言：PreperedStatement可以避免SQL注入的问题。
　　Statement会使数据库频繁编译SQL，可能造成数据库缓冲区溢出。PreparedStatement可对SQL进行预编译，从而提高数据库的执行效率。并且PreperedStatement对于sql中的参数，允许使用占位符的形式进行替换，简化sql语句的编写。

举例:

 PreperedStatement mi = Connection.preparedStatement();
 try{
 i = mi.executeUpdate();
  }catch(Exception e){
  if(i != )
 {
  System.out.println("修改不成功");
  }
  }

二:实际例子:

1: 编写index.jsp文件通过JSTL中的<c:redirect>标签指向servlet

 package com.ll;

 import java.io.IOException;
 import java.sql.*;
 import java.util.ArrayList;
 import java.util.List;

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

 import dao.Studentdao2;

 /**
  * Servlet implementation class GoodsServlet
  */
 @WebServlet("/GoodsServlet")
 public class GoodsServlet extends HttpServlet {
     private static final long serialVersionUID = 1L;

     /**
      * @see HttpServlet#HttpServlet()
      */
     public GoodsServlet() {
         super();
         // TODO Auto-generated constructor stub
     }

     /**
      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
         String action = request.getParameter("action");
         if(action.equals("zongjin")){

             try {
                 query(request,response);
             } catch (Exception e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
         }

     }

     /**
      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
      */
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // TODO Auto-generated method stub
     }

     public void query(HttpServletRequest request, HttpServletResponse response) throws Exception{
         Studentdao2 conn = new Studentdao2();
         String sql = "Select *from Student";

          /*
         //调用函数去向数据库中添加数据
           String addsql = "于海-19-软件1501-男";
           conn.addsql(addsql);
          */ 

         /*
          //删除数据库中的数据
         String strdelete = "Delete from Student Where 姓名 = '于海'";
         conn.deletesql(strdelete);
         */

         /*
          //修改数据库中的数据
         String update = "Update Student set 姓名='宗进' Where 姓名 = '小明' ";
         conn.updateSql(update);
         */

         ResultSet rs =conn.executeQuery1(sql);//调用自制函数来接受查询的结果
         List list = new ArrayList();
         while(rs.next())
         {
             Student f = new Student();
             //equals比较的结果为false是因为从数据库中返回的字符串为"宗进          "
             f.setBanji(rs.getString("班级"));
             f.setName(rs.getString("姓名"));
             f.setSex(rs.getString("性别"));
             f.setTime(rs.getString("年龄"));        

             list.add(f);

         }

         request.setAttribute("list", list);
         request.getRequestDispatcher("sql2.jsp").forward(request, response);

     }
     public String cat(String str){
         String[] arr = str.split(" ");
         String s = arr[];
         return s;

     }

 }

3.Servlet的web.xml文件

 <?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" xmlns:jsp="http://java.sun.com/xml/ns/javaee/jsp" 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">
   <display-name>JSTL</display-name>
   <welcome-file-list>
     <welcome-file>index.html</welcome-file>
     <welcome-file>index.htm</welcome-file>
     <welcome-file>index.jsp</welcome-file>
     <welcome-file>default.html</welcome-file>
     <welcome-file>default.htm</welcome-file>
     <welcome-file>default.jsp</welcome-file>
   </welcome-file-list>
   <jsp-config>
     <taglib>
       <taglib-uri>http://java.sun.com/jstl/fmt</taglib-uri>
       <taglib-location>/WEB-INF/tld/fmt.tld</taglib-location>
     </taglib>
     <taglib>
       <taglib-uri>http://java.sun.com/jstl/core</taglib-uri>
       <taglib-location>/WEB-INF/tld/c.tld</taglib-location>
     </taglib>
     <taglib>
       <taglib-uri>http://java.sun.com/jstl/sql</taglib-uri>
       <taglib-location>/WEB-INF/tld/sql.tld</taglib-location>
     </taglib>
     <taglib>
       <taglib-uri>http://java.sun.com/jstl/x</taglib-uri>
       <taglib-location>/WEB-INF/tld/x.tld</taglib-location>
     </taglib>
   </jsp-config>

   <servlet>
       <servlet-name>GoodsServlet</servlet-name>
       <servlet-class>com.ll.GoodsServlet</servlet-class>
   </servlet>

   <servlet-mapping>
        <servlet-name>GoodsServlet</servlet-name>
        <url-pattern>/com.ll.GoodsServlet</url-pattern>
   </servlet-mapping>

 </web-app>

4.创建一个用于连接数据库并且处理的类

 package dao;

 import java.io.InputStream;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.Properties;

 public class Studentdao2 {
      public Connection conn = null;
      public String url = null;
      public Statement stmt = null;
      public ResultSet rs = null;
      public static String propFilename = "Studentdao2.properties";
      private static Properties prop = new Properties();
      private static String  dbClassName = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
      private static String dbUrl = "jdbc:sqlserver://localhost:1433;DatabaseName=StudentManagement";
      private static String  addSql = "insert into Student values(?,?,?,?)";
      private static String updateSql = "update Student set 姓名=?,年龄=?,班级=?,性别=?";//用于整体修改数据库中的值
      public Studentdao2(){
          try{
             // InputStream in = getClass().getResourceAsStream(propFilename);
             // prop.load(in);
             // dbClassName = prop.getProperty("DB_URL",dbUrl);
             // dbUrl = prop.getProperty("DB_URL", dbUrl);
              Class.forName(dbClassName);
              conn = DriverManager.getConnection(dbUrl, "sa", "zongjin123");
              if(conn != null)
              {
                  System.out.println("连接成功");
              }
              else{
                  System.out.println("连接失败");
              }
              stmt = conn.createStatement();

          }catch(Exception e){
              e.printStackTrace();
          }

      }
     public ResultSet executeQuery1(String sql) throws Exception {
         // TODO Auto-generated method stub
         this.rs = this.stmt.executeQuery(sql);
         return this.rs;
     }
     public void addsql(String sql) throws Exception{
         PreparedStatement add = conn.prepareStatement(addSql);
         String[] shuju = sql.split("-");
         System.out.println(shuju[]);
         add.setString(, shuju[]);
         add.setString(,shuju[]);
         add.setString(,shuju[]);
         add.setString(, shuju[]);
         add.executeUpdate();
         add.close();
     }
     public void deletesql(String sql) throws Exception{
         int i = ;
         PreparedStatement delete = conn.prepareStatement(sql);
         try{
            i = delete.executeUpdate();
         }catch(Exception e){
             if(i != )
             {
                 System.out.println("删除失败");
             }
         }
         delete.close();
     }
     public void updateSql(String sql)throws Exception
     {
         PreparedStatement update = conn.prepareStatement(sql);
         //用于整体修改数据库中的值，但是一般直接用sq语句来进行操作数据库
         //update.setString(2, str);
         //String[] shuju = sql.split("-");
         //System.out.println(shuju[0]);
         //update.setString(1, shuju[0]);
         //update.setString(2,shuju[1]);
         //update.setString(3,shuju[2]);
         //update.setString(4, shuju[3]);
         update.executeUpdate();
         update.close();
     }

 }

5.编写用于存储数据的student类

 package com.ll;

 public class Student {
     private String name;
     private String time;
     private String banji;
     private String sex;
     public String getBanji() {
         return banji;
     }
     public void setBanji(String banji) {
         this.banji = banji;
     }

     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public String getTime() {
         return time;
     }
     public void setTime(String time) {
         this.time = time;
     }

     public String getSex() {
         return sex;
     }
     public void setSex(String sex) {
         this.sex = sex;
     }

 }

6运行index.jsp文件来运行