Java研学-web操作crud-编程知识

一思路

1 组件

页面显示：JSP
接受用户请求：Servlet
和数据库交互：MyBatis
在这里插入图片描述

2 基础准备

① 创建 web 项目，导入需要依赖的 jar 包,放入 web/WEB-INF/lib目录中在这里插入图片描述
② 创建数据库表

CREATE TABLE employee(
`id` bigint(11) NOT NULL auto_increment,`name` varchar(50) default NULL,`salary` double(10,2) default NULL,PRIMARY KEY  (`id`)
);INSERT INTO `employee` VALUES (1,'大黄', 8848.00);
INSERT INTO `employee` VALUES (2,'a黄', 8848.00);
INSERT INTO `employee` VALUES (3,'b黄', 8848.00);
INSERT INTO `employee` VALUES (4,'c黄', 8848.00);
INSERT INTO `employee` VALUES (5,'d黄', 8848.00);
INSERT INTO `employee` VALUES (6,'e黄', 8848.00);
INSERT INTO `employee` VALUES (7,'f黄', 8848.00);
INSERT INTO `employee` VALUES (8,'g黄', 8848.00);
INSERT INTO `employee` VALUES (9,'h黄', 8848.00);

③ 创建表对应的实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Employee {private Long id;private String name;private double salary;
}

④ MyBatis 配置文件实现

db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql:///play_web
jdbc.user=root
jdbc.password=root

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><properties resource="db.properties"></properties><typeAliases><package name="com.domain"/></typeAliases><environments default="dev"><environment id="dev"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="${jdbc.driver}"/><property name="url" value="${jdbc.url}"/><property name="username" value="${jdbc.user}"/><property name="password" value="${jdbc.password}"/></dataSource></environment></environments><mappers><mapper resource="mappers/EmployeeMapper.xml"></mapper></mappers>
</configuration>

⑤ 抽取工具类

MybatisUtil

package com.util;
public class MybatisUtil {private static  SqlSessionFactory factory=null;static {try {InputStream rs = Resources.getResourceAsStream("mybatis-config.xml");factory = new SqlSessionFactoryBuilder().build(rs);} catch (IOException e) {e.printStackTrace();}}public static SqlSession getSqlSession(){return factory.openSession(true);}
}

StringUtil – 判空

public class StringUtil {//判断输入的表单参数是否为空public static boolean hasLength(String s){return s!=null && s.trim().length()!=0;
}}

⑥ 根据实体类创建 dao 包以及接口

Dao

package com.dao;
import com.domain.Employee;
import java.util.List;
public interface EmployeeDao {// 增int add(Employee employee);// 删int delete(Long id);// 改int update(Employee employee);// 查全部List<Employee> list();// 根据id查Employee queryOne(Long id);
}

impl

package com.dao.impl;
import com.dao.EmployeeDao;
import com.domain.Employee;
import com.util.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import java.util.List;
public class EmployeeDaoImpl implements EmployeeDao {/*定义成员变量*/private SqlSession sqlSession= MybatisUtil.getSqlSession();@Overridepublic int add(Employee employee) {int row = sqlSession.insert("com.mapper.EmployeeMapper.add", employee);return row;}@Overridepublic int delete(Long id) {int row= sqlSession.delete("com.mapper.EmployeeMapper.delete",id);return row;}@Overridepublic int update(Employee employee) {int row= sqlSession.update("com.mapper.EmployeeMapper.update",employee);return row;}@Overridepublic List<Employee> list() {List<Employee> list = sqlSession.selectList("com.mapper.EmployeeMapper.list");return list;}@Overridepublic Employee queryOne(Long id) {Employee employee= sqlSession.selectOne("com.mapper.EmployeeMapper.selectOne", id);return employee;}
}

mapper

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mapper.EmployeeMapper"><!--增加商品--><insert id="add">insert into employee (name,salary)values(#{name},#{salary})</insert><!--修改--><update id="update">update employee set name=#{name},salary=#{salary} WHERE id=#{id}</update><!--删除--><delete id="delete">delete from employee WHERE id=#{id}</delete><!--根据id查询--><select id="queryOne" resultType="employee">SELECT * from employee WHERE id=#{id}</select><!--查询所有--><select id="list" resultType="employee">SELECT * from employee</select>
</mapper>

⑦ 日志文件 – log4j.properties

# Global logging configuration
log4j.rootLogger=ERROR, stdout
# MyBatis logging configuration...
log4j.logger.com.domain=TRACE
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

⑧ 生成测试类 EmployeeDaoImplTest，查看后台功能是否实现

package com.dao.impl;
import com.dao.EmployeeDao;
import com.domain.Employee;
import org.junit.Test;
import java.util.List;
public class EmployeeDaoImplTest {@Testpublic void add() {}@Testpublic void delete() {}@Testpublic void update() {}@Testpublic void list() {EmployeeDao employeeDao=new EmployeeDaoImpl();List<Employee> list = employeeDao.list();System.out.println(list);}@Testpublic void queryOne() {}
}

二前台实现

1 请求分发器

使用一个 Servlet 类来处理一张表的所有请求操作，即通过增加一个参数，用参数值来区分一个Servlet 中来区分不同的操作crud

package com.web.servlet;import com.dao.EmployeeDao;
import com.dao.impl.EmployeeDaoImpl;
import com.domain.Employee;
import com.util.StringUtil;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 java.io.IOException;
import java.util.List;@WebServlet("/employee")
public class EmployeeServlet extends HttpServlet {// 创建Dao对象private EmployeeDao employeeDao=new EmployeeDaoImpl();@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 设置编码格式req.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");// 获取请求分发的参数String cmd=req.getParameter("cmd");if("delete".equals(cmd)){// 调用删除delete(req,resp);}else if("input".equals(cmd)){// 跳转增加input(req,resp);}else if("saveOrUpdate".equals(cmd)){// 跳转修改saveOrUpdate(req,resp);}else {// 查所有list(req,resp);}}/*查询所有*/private void list(HttpServletRequest req, HttpServletResponse resp) {try {// 调用Dao查所有方法List<Employee> list=employeeDao.list();// 将查询结果存储到请求作用域req.setAttribute("list",list);// 转发到列表页面req.getRequestDispatcher("/WEB-INF/views/employee/list.jsp").forward(req,resp);} catch (ServletException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}}/*增加修改保存*/private void saveOrUpdate(HttpServletRequest req, HttpServletResponse resp) {//封装员工对象Employee employee=new Employee();/*将参数的获取及封装对象过程抽取成一个方法*/req2employee(req,employee);/*根据请求中是否携带id判断执行增加或者修改操作*/String id = req.getParameter("id");if (StringUtil.hasLength(id)){employee.setId(Long.valueOf(id));//执行修改employeeDao.update(employee);}else{//调用dao方法执行增加保存操作employeeDao.add(employee);}try {//跳转到查询resp.sendRedirect("/employee");} catch (IOException e) {e.printStackTrace();}}/*封装的获取请求参数的方法*/private void req2employee(HttpServletRequest req, Employee employee) {//获取请求中表单参数String name = req.getParameter("name");//验证输入的表单参数不能为空if (StringUtil.hasLength(name)){//设置员工的名称employee.setName(name);}String salary = req.getParameter("salary");if (StringUtil.hasLength(salary)){employee.setSalary(Double.valueOf(salary));}}/*跳转到编辑页面*/private void input(HttpServletRequest req, HttpServletResponse resp) {//根据请求中是否携带id判断是增加或者修改操作String id = req.getParameter("id");if (StringUtil.hasLength(id)){//请求中携带了id执行修改//根据id查询商品Employee employee = employeeDao.queryOne(Long.valueOf(id));//将查询的商品存储到作用域req.setAttribute("employee",employee);}try {//跳转到WEB-INF下面的页面：input.jspreq.getRequestDispatcher("/WEB-INF/views/employee/input.jsp").forward(req,resp);} catch (Exception e) {e.printStackTrace();}}/*删除*/private void delete(HttpServletRequest req, HttpServletResponse resp) {try {//获取目标idString id = req.getParameter("id");//调用删除方法int row = employeeDao.delete(Long.valueOf(id));//删除完毕跳转到查询resp.sendRedirect("/employee");} catch (IOException e) {e.printStackTrace();}}
}

2 前端crud实现

① input.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head><title>员工信息编辑页面</title>
</head>
<body>
<h3>员工信息编辑</h3>
<form action="/employee?cmd=saveOrUpdate" method="post"><input type="hidden" name="id" value="${employee.id}"><p>姓名：<input type="text" name="name" value="${employee.name}"></p><%--step="0.01"表示接受小数点后两位--%><p>工资：<input type="number" step="0.01" name="salary" value="${employee.salary}"></p><p><input type="submit" value="保存"></p>
</form>
</body>
</html>

② list.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%--引入核心标签库--%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head><title>员工信息页面</title>
</head>
<body>
<center><h3>员工列表</h3><p><a href="/employee?cmd=input">增加员工</a></p><table border="1px" cellpadding="0" cellspacing="0"width="800px"><tr><th>序号</th><th>姓名</th><th>工资</th><th>操作</th></tr><%--动态展示商品列表数据--%><c:forEach items="${list}" varStatus="vs" var="employee"><tr class="trClass"><td>${vs.count}</td><td>${employee.name}</td><td>${employee.salary}</td><td><a href="/employee?cmd=input&id=${employee.id}">修改员工信息</a>&nbsp;&nbsp;
<%--                    <a href="/product?cmd=delete&id=${product.id}">删除商品</a>--%><a href="#" onclick="deleteTr(${employee.id})">删除员工信息</a></td></tr></c:forEach></table>
</center><%--鼠标移动到当前行，实现背景颜色高亮显示--%>
<script>//获取所有的行元素：不包含表头var trs = document.getElementsByClassName("trClass");//遍历行元素集合for(var i=0;i<trs.length;i++){//鼠标移入：当前行高亮，背景变成灰色trs[i].onmouseover=function (){this.style.backgroundColor="gray";}//鼠标移出：恢复原来背景颜色trs[i].onmouseout=function (){this.style.backgroundColor="";}}
</script><%--删除确认表--%>
<script>function deleteTr(id){//确认删除var b= window.confirm("确认删除选中的员工信息吗？");if(b){//确定删除，执行后台删除操作window.location="/employee?cmd=delete&id="+id;}}
</script>
</body>
</html>

③ index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html><head><title>员工信息管理</title></head><body><a href="/employee">员工信息管理</a></body>
</html>