servlet增删改查

Servlet

使用Servlet进行增删改查

步骤

1．  导入以下几个jar包到WEB-INF下的lib包里，必要时build path，其中jstl.jar和standard.jar是使用jstl要用的（eclipse中）

2．  写对应的dao,service,以及实现类

3．  写对应的servlet类，必须继承HttpServlet类

1. 在此servlet类里加私有的service实现类;
2. 添加doPost()和doGet方法：一般是在doPost()里写具体操作代码，doGet()方法里调用doPost,这样，不管提交方式是post还是get，都可以访问；
3. doPost()方法里要先加

request.setCharacterEncoding("utf-8");

       response.setContentType("text/html;charset=utf-8");

1. 取参和传参，转发和重定向

取参：

String age1=request.getParameter("age");

       int age = Integer.parseInt(age1);

传参：

request.setAttribute("emp", emp);

转发：

request.getRequestDispatcher("/emp.jsp").forward(request, response);

重定向：

response.sendRedirect(request.getContextPath()+"/error.jsp");

5配置web.xml，写对应的servlet和其映射

访问时：先通过url定位到web.xml里servlet的url-pattern,再对应到servlet-name，再找到对应的servlet类，根据访问时提交的方法调用相应的doPost()或者doGet()方法

6.写对应的前台页面

取后台传过来的数据：${ }

提交的url路径：

<form  action="/servletTest/updateEmp" method="post"></form>

<a  href="/servletTest/deleteEmp?id=${emp.id }">删除</a>

示例代码

DbUtil.java

package util;

import org.apache.commons.dbutils.QueryRunner;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class DbUtil {

private static ComboPooledDataSource ds=new ComboPooledDataSource();

public static QueryRunner getQueryRunner(){
QueryRunner qr = new QueryRunner(ds);
return qr;
}

}

c3p0-config.xml

<c3p0-config>
<default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://localhost/test</property>
<property name="user">root</property>
<property name="password"></property>
<property name="initialPoolSize">5</property>
<property name="maxPoolSize">10</property>
</default-config>
</c3p0-config>

EmpDao.java

package dao;

import java.util.List;

import entity.Emp;

public interface EmpDao {

public int add(Emp emp);
public int delete(int id);
public int update(Emp emp);
public Emp find(int id);
public List<Emp> findAll();
}

EmpDaoImpl.java

package dao.impl;

import java.sql.SQLException;
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 util.DbUtil;
import dao.EmpDao;
import entity.Emp;

public class EmpDaoImpl implements EmpDao {

QueryRunner qr = DbUtil.getQueryRunner();
@Override
public int add(Emp emp) {
String sql="insert into emp(age,name) values(?,?) ";
int num=0;
try {
num = qr.update(sql, emp.getAge(),emp.getName());
} catch (SQLException e) {
e.printStackTrace();
}
return num;
}
@Override
public List<Emp> findAll() {
String sql="select*from emp";
List<Emp> emps=null;
try {
emps=qr.query(sql, new BeanListHandler<Emp>(Emp.class));
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return emps;
}
@Override
public int delete(int id) {
String sql="delete from emp where id="+id;
int num=0;
try {
num=qr.update(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return num;
}
@Override
public int update(Emp emp) {
String sql="update emp set name=?,age=? where id=?";
System.out.println("sql---------"+sql);
int num=0;
try {
num=qr.update(sql, emp.getName(),emp.getAge(),emp.getId());
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return num;
}
@Override
public Emp find(int id) {
String sql="select * from emp where id="+id;
Emp emp=null;
try {
emp=qr.query(sql, new BeanHandler<Emp>(Emp.class));
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return emp;
}

}

EmpService.java

package service;

import java.util.List;

import entity.Emp;

public interface EmpService {

public int addEmp(Emp emp);
public List<Emp> findAll();
public int delete(int id);
public int update(Emp emp);
public Emp find(int id);
}

EmpServiceImpl.java

package service.impl;

import java.util.List;

import service.EmpService;
import dao.impl.EmpDaoImpl;
import entity.Emp;

public class EmpServiceImpl implements EmpService {

private EmpDaoImpl empDao=new EmpDaoImpl();
@Override
public int addEmp(Emp emp) {
int num = empDao.add(emp);
return num;
}
@Override
public List<Emp> findAll() {

return empDao.findAll();
}
@Override
public int delete(int id) {

return empDao.delete(id);
}
@Override
public int update(Emp emp) {

return empDao.update(emp);
}
@Override
public Emp find(int id) {
return empDao.find(id);
}

}

AddEmpServlet.java

package servlet;

import java.io.IOException;

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

import service.impl.EmpServiceImpl;
import entity.Emp;

public class AddEmpServlet extends HttpServlet {

private EmpServiceImpl empService=new EmpServiceImpl();
@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
String age1=request.getParameter("age");
int age = Integer.parseInt(age1);
String name = request.getParameter("name");
Emp emp=new Emp();
emp.setAge(age);
emp.setName(name);
int num = empService.addEmp(emp);
if(num>0){
response.sendRedirect(request.getContextPath()+"/empList");
}else{
response.sendRedirect(request.getContextPath()+"/error.jsp");
}
}
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);;
}
}

DeleteEmpServlet.java

package servlet;

import java.io.IOException;

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

import service.impl.EmpServiceImpl;
import entity.Emp;

public class DeleteEmpServlet extends HttpServlet {

private EmpServiceImpl empService=new EmpServiceImpl();

@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
String id1 = request.getParameter("id");
Integer id=Integer.parseInt(id1);
System.out.println("进入删除,id="+id);
int num = empService.delete(id);
System.out.println("删除？---"+num);
if(num>0){
response.sendRedirect(request.getContextPath()+"/empList");
}else{
response.sendRedirect("/error.jsp");
}
}

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

//修改时，先找到要修改的对象，再转发到需要修改的页面，显示要修改的对象信息，然后提交时修改

FindUpdEmpServlet .java

package servlet;

import java.io.IOException;

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

import entity.Emp;
import service.impl.EmpServiceImpl;

public class FindUpdEmpServlet extends HttpServlet {

private EmpServiceImpl empService=new EmpServiceImpl();

@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
Integer id=Integer.parseInt(request.getParameter("id"));
Emp emp = empService.find(id);
System.out.println("要修改的emp"+emp.getName());
if(emp!=null){
request.setAttribute("emp", emp);
request.getRequestDispatcher("/update.jsp").forward(request, response);;
}else{
response.sendRedirect(request.getContextPath()+"/error.jsp");
}
}
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}

}

UpdateEmpServlet.java

package servlet;

import java.io.IOException;

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

import service.impl.EmpServiceImpl;
import entity.Emp;

public class UpdateEmpServlet extends HttpServlet {

private EmpServiceImpl empService=new EmpServiceImpl();

@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
String id1 = request.getParameter("id");
Integer id=Integer.parseInt(id1);
String name = request.getParameter("name");
String age1 = request.getParameter("age");
Integer age=Integer.parseInt(age1);
Emp emp=new Emp();
emp.setId(id);
emp.setAge(age);
emp.setName(name);
//empService.find(id);
int num = empService.update(emp);
if(num>0){
response.sendRedirect(request.getContextPath()+"/empList");
}else{
response.sendRedirect("/error.jsp");
}
}
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}

}

FindEmpServlet.java

package servlet;

import java.io.IOException;

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

import entity.Emp;
import service.impl.EmpServiceImpl;

public class FindEmpServlet extends HttpServlet {

private EmpServiceImpl empService=new EmpServiceImpl();
@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
Integer id=Integer.parseInt(request.getParameter("id"));
Emp emp = empService.find(id);
System.out.println("emp---"+emp.getName()+"---"+emp.getAge());
if(emp!= null){
request.setAttribute("emp", emp);
request.getRequestDispatcher("/emp.jsp").forward(request, response);
}else{
response.sendRedirect(request.getContextPath()+"/error.jsp");
}
}
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
}

FindEmpsServlet.java

package servlet;

import java.io.IOException;
import java.util.List;

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

import entity.Emp;
import service.impl.EmpServiceImpl;

public class FindEmpsServlet extends HttpServlet {

private EmpServiceImpl empService=new EmpServiceImpl();

@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
List<Emp> emps = empService.findAll();
if(emps!=null){
request.setAttribute("emps", emps);
request.getRequestDispatcher("/list.jsp").forward(request, response);
}else{
response.sendRedirect(request.getContextPath()+"/error.jsp");
}
}
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
}

web.xml

<?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_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>servletTest</display-name>
<servlet>
<servlet-name>addEmp</servlet-name>
<servlet-class>servlet.AddEmpServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>deleteEmp</servlet-name>
<servlet-class>servlet.DeleteEmpServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>findUpdEmp</servlet-name>
<servlet-class>servlet.FindUpdEmpServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>updateEmp</servlet-name>
<servlet-class>servlet.UpdateEmpServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>findEmp</servlet-name>
<servlet-class>servlet.FindEmpServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>empList</servlet-name>
<servlet-class>servlet.FindEmpsServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>addEmp</servlet-name>
<url-pattern>/addEmp</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>deleteEmp</servlet-name>
<url-pattern>/deleteEmp</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>findUpdEmp</servlet-name>
<url-pattern>/findUpdEmp</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>updateEmp</servlet-name>
<url-pattern>/updateEmp</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>findEmp</servlet-name>
<url-pattern>/findEmp</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>empList</servlet-name>
<url-pattern>/empList</url-pattern>
</servlet-mapping>

<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

前台页面

add.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>添加员工</title>
</head>
<body>
<form action="/servletTest/addEmp" method="post">
姓名：<input type="text" name="name"/><p>
年龄：<input type="text" name="age"/><p>
<input type="submit" value="添加"/>
</form>
</body>
</html>

list.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!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>员工列表</title>
</head>
<body>
添加成功
<table>
<tr >
<td colspan="3">
<a href="index.jsp">添加</a>
</td>
</tr>
<tr>
<th>编号</th>
<th>年龄</th>
<th>age</th>
<th colspan="3">操作</th>
</tr>
<!--items里面写${requestScope.emps}也可以 -->
<c:forEach items="${emps }" var="emp" varStatus="vs">
<tr>
<td>${emp.id }</td>
<td>${emp.name }</td>
<td>${emp.age }</td>
<td><a href="/servletTest/deleteEmp?id=${emp.id }">删除</a></td>
<td><a href="/servletTest/findUpdEmp?id=${emp.id }">修改</a></td>
<td><a href="/servletTest/findEmp?id=${emp.id }">查看</a></td>
</tr>

</c:forEach>
</table>
</body>
</html>

emp.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>
编号:${emp.id }<p>
姓名：${emp.name }<p>
年龄：${emp.age }
</body>
</html>

update.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>修改员工</title>
</head>
<body>
<form action="/servletTest/updateEmp" method="post">
编号：<input type="text" name="id" value="${emp.id }" readonly="readonly"/><p>
姓名：<input type="text" name="name" value="${emp.name }"/><p>
年龄:<input type="text" name="age" value="${emp.age }"/><p>
<input type="submit" value="提交"/>
</form>
</body>
</html>

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>
<h1>出错了</h1>
</body>
</html>