MVC模式：实现数据库中数据的增删改查功能

*.数据库连接池c3p0，连接mysql数据库；

*.Jquery使用，删除时跳出框，确定是否要删除；

*.使用EL和JSTL，简化在jsp页面中插入的java语言

1.连接数据库

（1）导入连接数据库连接池的开源架包和EL和JSTL的架包（在lib目录下导入）

c3p0-0.9.1.2jar

commons-dbutils-1.3jar

mysql-connector-java-5.1jar

jstl.jar

standard.jar

（2）在src目录下建立一个c3p0-config.xml文件，存放数据库连接池的变量：

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>

<named-config name="mvcapp">

<!-- 指定连接数据源的基本属性 -->
<property name="user">root</property>
<property name="password">lxn123</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql:///test</property>

<!-- 若数据库中连接数不足时, 一次向数据库服务器申请多少个连接 -->
<property name="acquireIncrement">5</property>
<!-- 初始化数据库连接池时连接的数量 -->
<property name="initialPoolSize">10</property>
<!-- 数据库连接池中的最小的数据库连接数 -->
<property name="minPoolSize">10</property>
<!-- 数据库连接池中的最大的数据库连接数 -->
<property name="maxPoolSize">50</property>

<!-- C3P0 数据库连接池可以维护的 Statement 的个数 -->
<property name="maxStatements">20</property>
<!-- 每个连接同时可以使用的 Statement 对象的个数 -->
<property name="maxStatementsPerConnection">5</property>

</named-config>

</c3p0-config>

(2)连接数据库连接池的类：JdbcUtils

package com.lanqiao.javatest;

import java.sql.Connection;
import java.sql.SQLException;

import org.junit.Test;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JdbcUtils {
    //实现数据库连接池的方法类

    //该静态代码块只执行一次
    private static ComboPooledDataSource dataSource=null;
    static{
        dataSource=new ComboPooledDataSource("mvcapp");
    }
    public static Connection getConnection() throws SQLException{
        return dataSource.getConnection();

    }

    @Test
    //测试数据库连接池是否连接成功
    public void testT() throws SQLException{
        System.out.println(getConnection());
    }

    //释放connection连接
    public static void releaseConnection(Connection connection){
        try {
            if(connection!=null){
                connection.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2.建立customer类，对数据库中的属性进行封装；

package com.lanqiao.javatest;

public class Customer {
    private Integer id;
    private String name;
    private String address;
    private String phone;
    public Customer() {
        super();
        // TODO Auto-generated constructor stub
    }

    public Customer(String name, String address, String phone) {

        this.name = name;
        this.address = address;
        this.phone = phone;
    }

    public Customer(Integer id, String name, String address, String phone) {
        super();
        this.id = id;
        this.name = name;
        this.address = address;
        this.phone = phone;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    @Override
    public String toString() {
        return "Person [id=" + id + ", name=" + name + ", address=" + address + ", phone=" + phone + "]";
    }

}

3.建立CriteriaCustomer类，对数据库中的部分数据进行封装，便于模糊查询使用

package com.lanqiao.javatest;

//模糊查询的类
public class CriteriaCustomer {
    private String name;
    private String address;
    private String phone;

    public CriteriaCustomer() {
        super();
    }

    public CriteriaCustomer(String name, String address, String phone) {
        super();
        this.name = name;
        this.address = address;
        this.phone = phone;
    }

    public String getName() {
        if (name==null) {
            name="%%";
        }
        else{
            name="%"+name+"%";
        }
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAddress() {
        if (address==null) {
            address="%%";
        }
        else{
            address="%"+address+"%";
        }
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getPhone() {
        if (phone==null) {
            phone="%%";
        }
        else{
            phone="%"+phone+"%";
        }
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

}

4.在src目录下建立一个接口类：CustomerDAO，对一些方法进行了封装；

package com.lanqiao.javatest;

import java.util.List;

//创建以CustomerDAO接口，可以实现其他类的调用
public interface CustomerDAO {

    //模糊查询方法
    public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer cc);

    //查询的方法，将数据库的所有数据放在list集合中，并实现输出的查询
    public List<Customer> getAll();

    //
    public void save(Customer customer);

    //通过jsp超链接里面？后面的id,获取该id下的各属性的值
    public Customer get(Integer id);

    //通过jsp超链接里面？后面的id,并且实现删除的功能
    public void delete(Integer id);

    //返回和该name相等的个数
    public long getCountWithName(String name);

    void update(Customer customer);
}

5.建一个DAO类，有得到某一个类方法明的反射方法，实现对数据的增删改查的方法

package com.lanqiao.javatest;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.Connection;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

/*
 * 封装了基本的增删改查方法，以供子类继承使用；
 * 当前dao没有事务，直接在方法中获取数据库的链接
 * */
public class DAO <T>{

    //这个是线程安全的
    private QueryRunner queryRunner=new QueryRunner();

     private Class<T> clazz;

     //类的构造方法
     public DAO() {
         //得到父类带泛型的类型
         //type类型导包为import java.lang.reflect.Type;反射类型里面的
         //反射。。。。。。Type所有超级类接口，ParameterizedType表示参数化类型,参数化类型在反射方法首次需要时创建（在此包中指定）。
         //当创建参数化类型 p 时，p 实例化的一般类型声明会被解析，并且按递归方式创建 p 的所有类型参数。

        Type superClass=getClass().getGenericSuperclass();
        if (superClass instanceof ParameterizedType) {
            ParameterizedType parameterizedType=(ParameterizedType) superClass;

            // getActualTypeArguments():返回表示此类型实际类型参数的 Type 对象的数组。
            Type[] typeArgs=parameterizedType.getActualTypeArguments();
            if (typeArgs!=null && typeArgs.length>0) {
                if (typeArgs[0] instanceof Class) {
                    clazz=(Class<T>) typeArgs[0];
                }
            }
        }
    }

    //返回某一字段的值：比如返回某一条记录的customerName,或返回有多少条记录
     public <E> E getForValue(String sql,Object...args){
         Connection connection=null;
        try {
            connection=JdbcUtils.getConnection();
            return (E) queryRunner.query(connection,sql,new ScalarHandler(),args);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.releaseConnection(connection);
        }
        return null;
     }

     //返回所对应的list集合,获得的是一组的
     public List<T> getForList(String sql,Object...args){
         Connection connection=null;
        try {
            connection=JdbcUtils.getConnection();
            return queryRunner.query(connection,sql,new BeanListHandler<>(clazz),args);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.releaseConnection(connection);
        }
        return null;
     }

    //返回对应的T的一个实体类的对象
    public T get(String sql,Object...args){

        Connection connection=null;
        try {
            connection=JdbcUtils.getConnection();
            return queryRunner.query(connection,sql,new BeanHandler<>(clazz),args);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.releaseConnection(connection);
        }
        return null;
    }

    //该方法封装了增删改操作
    public void update(String sql,Object...args){
        Connection connection=null;

        try {
            connection=JdbcUtils.getConnection();
            queryRunner.update(connection, sql, args);

        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.releaseConnection(connection);
        }
    }
}

6.建立一个类：CustomerDAOJdbcImpl 继承于父类 DAO<Customer> 和继承于接口 CustomerDAO，增删改查方法和模糊查询的方法；

package com.lanqiao.javatest;

import java.util.List;

import com.lanqiao.javatest.CriteriaCustomer;
import com.lanqiao.javatest.CustomerDAO;
import com.lanqiao.javatest.DAO;

//实现各个功能的类
public class CustomerDAOJdbcImpl extends DAO<Customer> implements CustomerDAO{

    @Override
    //模糊查询的方法
    public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer cc) {
        String sql="select id,name,address,phone from customer "
                + "where name like ? and address like ? and phone like ?";
        //修改了CriteriaCustomer的get方法，使其返回的字符串中含有%%
        return getForList(sql,cc.getName(),cc.getAddress(),cc.getPhone());
    }

    @Override
    //获取整个数据库中的所有数据
    public List<Customer> getAll() {
        String sql1="select id,name,address,phone from customer";
        return getForList(sql1);
    }

    @Override
    //插入数据到数据库的方法
    public void save(Customer customer) {
        String sql2="insert into customer(name,address,phone) values(?,?,?)";
        update(sql2, customer.getName(),customer.getAddress(),customer.getPhone());
    }

    @Override
    //获取某个数据
    public Customer get(Integer id) {
        String sql3="select id,name,address,phone from customer where id=?";
        return get(sql3,id);
    }

    @Override
    //删除id=?的数据
    public void delete(Integer id) {
        String sql4="delete from customer where id=?";
        update(sql4, id);
    }

    @Override
    //用名字获取count(name)，即获取用户的数量
    public long getCountWithName(String name) {
        String sql5="select count(name) from customer where name=?";
        return getForValue(sql5, name);
    }

    @Override
    public void update(Customer customer) {
        String sql = "UPDATE customer SET name = ?, address = ?, phone = ? " +
                "WHERE id = ?";
        update(sql, customer.getName(), customer.getAddress(),
                customer.getPhone(), customer.getId());
    }

}

7.建立一个Servlet类：doGet和doPost方法；

package com.lanqiao.javatest1;

import java.io.IOException;
import java.lang.reflect.Method;
import java.util.List;

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

import com.lanqiao.javatest.CriteriaCustomer;
import com.lanqiao.javatest.Customer;
import com.lanqiao.javatest.CustomerDAO;
import com.lanqiao.javatest.CustomerDAOJdbcImpl;

public class CustomerServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    private CustomerDAO customerDAO=new CustomerDAOJdbcImpl();

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

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //利用反射，接受多个以.do结尾的请求

        //1.变量 servletPath获取所有后边带.do的方法名和.do ,例如这个/pass.do
        String servletPath=request.getServletPath();

        //2.在字符串后面除去.do这个字符
        String methodName=servletPath.substring(1);
        methodName=methodName.substring(0,methodName.length()-3);
        //System.out.println(methodName);
        try {
            //反射获取该类的该方法
            Method method=getClass().getDeclaredMethod
                    (methodName, HttpServletRequest.class,HttpServletResponse.class);
            //这里面的this指通过这个方法的到方法名字，并且输出，及this指methodName的到的方法名字
            method.invoke(this,request,response);

        } catch (Exception e) {
            //如果出现错误，去error页面
            response.sendRedirect("error.jsp");
        } 

    }

    //查询方法
    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取模糊查询的请求参数
        String name=request.getParameter("name");
        String address=request.getParameter("address");
        String phone=request.getParameter("phone");

        //把请求参数封装为一个CriteriaCustomer对象
        CriteriaCustomer cc=new CriteriaCustomer(name,address,phone);

        //1.调用CustomerDAO的getForListWithCriteriaCustomer(cc)方法得到lists的集合
        List<Customer> lists=customerDAO.getForListWithCriteriaCustomer(cc);

        //2.把list集合放到request中
        request.setAttribute("list", lists);

        //3.转发页面到index.jsp(不能使用重定向) /代表的是根目录下的jsp文件；
        request.getRequestDispatcher("/index.jsp").forward(request, response);
    }

    //插入数据的方法：
    private void addCustomer(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException{

        //1.获取表单参数，name,address,phone
        String name=request.getParameter("name");
        String address=request.getParameter("address");
        String phone=request.getParameter("phone");

        //检验名字是否已经被占用了:调用CustomerDAO的getCountWithName方法，获取name参数是否大于0，如果大于....
        //并且消息可以回显:value="<%=request.getParameter("name")==null ? "" :%>"
        long count=customerDAO.getCountWithName(name);

        if (count>0) {
            request.setAttribute("message","用户名"+name+"已经被占用了，请重新选择！！！");

            //名字重复了，请求的转发到/newcustomer.jsp
            request.getRequestDispatcher("/newcustomer.jsp").forward(request, response);
            //结束方法
            return ;
        }

        //2.若验证通过的话，把表单参数封装为一个customer的对象
        Customer customer=new Customer(name,address,phone); 

        //3.调用CustomerDAO的save方法执行保存
        customerDAO.save(customer);

        //数据插入成功后，请求的转发到newcustomer.jsp
        //request.getRequestDispatcher("/newcustomer.jsp").forward(request, response);

        //4.数据插入成功后，重定向到success.jsp页面：使用重定向可以避免出现表单的重复提交问题.
        response.sendRedirect("success.jsp");

    }

    private void delete(HttpServletRequest request, HttpServletResponse response) throws IOException {
        //1.获取请求的id
        String idStr=request.getParameter("id");
        int id=0;
        try {
            id=Integer.parseInt(idStr);
            //2.调用CustomerDAO的getId()方法执行删除
            customerDAO.delete(id);
        } catch (Exception e) {
            response.sendRedirect("query.do");
        }
        //重定向的页面jsp,其前面不用加"/"
        response.sendRedirect("success.jsp");
    }

    //修改数据表里的数据
    private void edit(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //出现了所查询的数据不存在的错误显示到error.jsp页面
        String forwardPath="/error.jsp";

        //1.获取请求的id
        String idStr=request.getParameter("id");

        //2. 调用 CustomerDAO 的 customerDAO.get(id) 获取和 id 对应的 Customer 对象 customer
        try {

            Customer customer=customerDAO.get(Integer.parseInt(idStr));
            //如果数据存在的跳转到updatecustomer.jsp页面，进行修改数据
            if(customer!=null){
                forwardPath="/updatecustomer.jsp";
                //将数据放到request请求的转发的里面
                request.setAttribute("customer", customer);
            }
        } catch (Exception e) {
            System.out.println("fsdlkf");
        }

        //4. 响应 updatecustomer.jsp 页面: 转发.
        request.getRequestDispatcher(forwardPath).forward(request, response);
    }

    private void update(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //1. 获取表单参数: id, name, address, phone, oldName
        String id=request.getParameter("id");
        String name=request.getParameter("name");
        String address=request.getParameter("address");
        String phone=request.getParameter("phone");
        String oldName=request.getParameter("oldName");

        //2. 检验 name 是否已经被占用:

        //2.1 比较 name 和 oldName 是否相同, 若相同说明 name 可用.
        //2.1 若不相同, 则调用 CustomerDAO 的 getCountWithName(String name) 获取 name 在数据库中是否存在
        if(!oldName.equalsIgnoreCase(name)){
            long count=customerDAO.getCountWithName(name);

            //2.2 若返回值大于 0, 则响应 updatecustomer.jsp 页面: 通过转发的方式来响应 newcustomer.jsp
            if (count>0) {
                //2.2.1 在 updatecustomer.jsp 页面显示一个错误消息: 用户名 name 已经被占用, 请重新选择!
                //在 request 中放入一个属性 message: 用户名 name 已经被占用, 请重新选择!,
                //在页面上通过 request.getAttribute("message") 的方式来显示
                request.setAttribute("message", "用户名"+name+"已经被占用，请重现选择！！！");

                //2.2.2 newcustomer.jsp 的表单值可以回显.
                //address, phone 显示提交表单的新的值, 而 name 显示 oldName, 而不是新提交的 name

                //2.2.3 结束方法: return
                request.getRequestDispatcher("updatecustomer.jsp").forward(request, response);
                return ;
            }
        }
        //3. 若验证通过, 则把表单参数封装为一个 Customer 对象 customer
        Customer customer=new Customer(name,address,phone);
        customer.setId(Integer.parseInt(id));

        //4. 调用 CustomerDAO 的  update(Customer customer) 执行更新操作
        customerDAO.update(customer);

        //5. 重定向到 query.do
        response.sendRedirect("query.do");
    }

}

8.在WEB-INF下的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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>day-11</display-name>
  <servlet>
    <description></description>
    <display-name>CustomerServlet1</display-name>
    <servlet-name>CustomerServlet1</servlet-name>
    <servlet-class>com.lanqiao.javatest1.CustomerServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>CustomerServlet1</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>
</web-app>

9.几个jsp页面；

(1)index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>    

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript" src="scripts/jquery-1.7.2.js"></script>
<script type="text/javascript">

    $(function(){
        $(".delete12").click(function(){
            var content = $(this).parent().parent().find("td:eq(1)").text();
            var flag = confirm("确定要是删除" + content + "的信息吗?");
            return flag;
        });
    });

</script>
</head>
<body>

    <form action="query.do" method="post">
        <table>
            <tr>
                <td>Name:</td>
                <td><input type="text" name="name"/></td>
            </tr>
            <tr>
                <td>Address:</td>
                <td><input type="text" name="address"/></td>
            </tr>
            <tr>
                <td>Phone:</td>
                <td><input type="text" name="phone"/></td>
            </tr>
            <tr>
                <td><input type="submit" value="Query"/></td>
                <td><a href="newcustomer.jsp">Add New Customer</a></td>
            </tr>
        </table>
    </form>

    <br><br>

    <c:if test="${!empty requestScope.list }">

        <hr>
        <br><br>

        <table border="1" cellpadding="10" cellspacing="0">
            <tr>
                <th>id</th>
                <th>name</th>
                <th>address</th>
                <th>phone</th>
                <th>update</th>
                <th>delete</th>
            </tr>

            <c:forEach items="${requestScope.list }" var="cust">

                    <tr>
                        <td>${cust.id }</td>
                        <td>${cust.name }</td>
                        <td>${cust.address }</td>
                        <td>${cust.phone }</td>
                        <td>
                            <c:url value="/edit.do" var="editurl">
                                <c:param name="id" value="${cust.id }"></c:param>
                            </c:url>
                            <a href="${editurl }">UPDATE</a>
                        <td/>

                            <c:url value="/delete.do" var="deleteurl">
                                <c:param name="id" value="${cust.id }"></c:param>
                            </c:url>
                            <a href="${deleteurl }" class="delete12">DELETE</a>

                    </tr>

            </c:forEach>

        </table>
    </c:if>

</body>
</html>

(2)newcustomer.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>

    <c:if test="${requestScope.message != null }">
        <br>
        <font color="red">${requestScope.message }</font>
        <br>
        <br>
    </c:if>

    <form action="addCustomer.do" method="post">
        <table>
            <tr>
                <td>Name:</td>
                <td><input type="text" name="name" value="${param.name }"/></td>
            </tr>
            <tr>
                <td>Address:</td>
                <td><input type="text" name="address" value="${param.address }"/></td>
            </tr>
            <tr>
                <td>Phone:</td>
                <td><input type="text" name="phone" value="${param.phone }"/></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="Submit"/></td>
            </tr>
        </table>
    </form>

</body>
</html>

(3)updatecustomer.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>    

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>

    <c:if test="${requestScope.message != null }">
        <br>
        <font color="red">${requestScope.message }</font>
        <br>
        <br>
    </c:if>

    <c:set var="id" value="${customer != null ? customer.id : param.id }"></c:set>
    <c:set var="oldName" value="${customer != null ? customer.name : param.oldName }"></c:set>
    <c:set var="name" value="${customer != null ? customer.name : param.oldName }"></c:set>
    <c:set var="address" value="${customer != null ? customer.address : param.address }"></c:set>
    <c:set var="phone" value="${customer != null ? customer.phone : param.phone }"></c:set>

    <form action="update.do" method="post">

        <input type="hidden" name="id" value="${id }"/>
        <input type="hidden" name="oldName" value="${oldName }"/>

        <table>
            <tr>
                <td>Name:</td>
                <td><input type="text" name="name"
                    value="${name }"/></td>
            </tr>
            <tr>
                <td>Address:</td>
                <td><input type="text" name="address"
                    value="${address }"/></td>
            </tr>
            <tr>
                <td>Phone:</td>
                <td><input type="text" name="phone"
                    value="${phone }"/></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="Submit"/></td>
            </tr>
        </table>
    </form>

</body>
</html>

(4)success.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <h2>操作成功！！！</h2>
    <a href="index.jsp">Return....</a>
</body>
</html>

(5)error.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <h3>不好意思页面无法打开！！！</h3>
</body>
</html>