maven搭建项目--实现mybatis增删改差、一对多及一对一关系

1、创建maven项目

2、配置pom.xml，引入相应的jar包

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>
<groupId>com.danni</groupId>
<artifactId>mybatis-maven</artifactId>
<version>0.0.1-SNAPSHOT</version>

<dependencies>
<!-- mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.5</version>
</dependency>

<!-- java连接数据库的包 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-Java</artifactId>
<version>5.1.6</version>
</dependency>

<!-- 日志包 -->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.12</version>
</dependency>
</dependencies>
</project>

3、在Eclipse安装mybatis generator自动生成工具

（1）下载mybatis生成架包工具MyBatis_Generator_1.3.1.zip，解压jar包把features、plugins文件夹下的架包分别拷贝到eclipse安装目录下的features、plugins文件夹（复制和替换eclipse原有的这两个文件夹）。然后重启eclipse。



（2）在pom.xml中添加mybatis-generator-maven-plugin的jar包

<!-- mybatis generator自动生成jar包 -->
<dependency>
<groupId>org.mybatis.generator</groupId>
<artifactId>mybatis-generator-maven-plugin</artifactId>
<version>1.3.2</version>
<type>maven-plugin</type>
</dependency>

（3）配置generator.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN" "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
<!-- 数据库驱动包位置 (改成自己存放的具体路径) -->
<classPathEntry location="D:/softwaretools/someNeeded/mysql-connector-java-5.1.34.jar" />

<context id="DB2Tables" targetRuntime="MyBatis3">
<commentGenerator>
<property name="suppressAllComments" value="true" />
</commentGenerator>

<!-- 数据库链接UR
4000
L、用户名、密码 -->
<jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://localhost:3306/student" userId="root" password="root"> </jdbcConnection>

<javaTypeResolver>
<property name="forceBigDecimals" value="false" />
</javaTypeResolver>

<!-- 生成模型的包名和位置 ，targetPackage：包名，targetProject：你的项目名-->
<javaModelGenerator targetPackage="com.danni.model.entity" targetProject="mybatis-maven">
<property name="enableSubPackages" value="true" />
<property name="trimStrings" value="true" />
</javaModelGenerator>

<!-- 生成的映射文件包名和位置 -->
<sqlMapGenerator targetPackage="com.danni.model.dao" targetProject="mybatis-maven">
<property name="enableSubPackages" value="true" />
</sqlMapGenerator>

<!-- 生成DAO的包名和位置 -->
<javaClientGenerator type="XMLMAPPER" targetPackage="com.danni.model.dao" targetProject="mybatis-maven">
<property name="enableSubPackages" value="true" />
</javaClientGenerator>

<!-- tableName：数据库中的表名，domainObjectName：表名对应的类名 -->
<table tableName="admins" domainObjectName="Admins" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false" />
<table tableName="employee" domainObjectName="Employee" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false" />
<table tableName="department" domainObjectName="Department" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false" />
</context>
</generatorConfiguration>

（4）选中generator.xml，右键选择Generate MyBatis/IBATIS Artifacts，点击即可生成代码文件。

4、编写数据库和日志的properties文件

jdbc.properties

driver = com.mysql.jdbc.Driver
url = jdbc:mysql:///student?characterEncoding=utf-8
username = root
password = root

log4j.properties

log4j.rootLogger=DEBUG, Console
#Console
log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
#log4j.appender.Console.layout.ConversionPattern=%d [%t] %-5p [%c] - %m%n
log4j.logger.java.sql.ResultSet=INFO
log4j.logger.org.apache=INFO
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

5、配置mybatis配置文件：mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!-- 加载数据库的properties文件 -->
<properties resource="jdbc.properties"/>

<settings>
<setting name="logImpl" value="LOG4J" />
<!-- 开启二级缓存(总开关) -->
<setting name="cacheEnabled" value="true"/>
</settings>

<!-- 配置别名 -->
<typeAliases>
<typeAlias type="com.danni.model.entity.Admins" alias="Admins"/>
<typeAlias type="com.danni.model.entity.Department" alias="Department"/>
<typeAlias type="com.danni.model.entity.Employee" alias="Employee"/>
</typeAliases>

<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${driver}" />
<property name="url" value="${url}" />
<property name="username" value="${username}" />
<property name="password" value="${password}" />
</dataSource>
</environment>
</environments>

<mappers>
<mapper resource="com/danni/model/dao/AdminsMapper.xml" />
<mapper resource="com/danni/model/dao/DepartmentMapper.xml" />
<mapper resource="com/danni/model/dao/EmployeeMapper.xml" />
</mappers>
</configuration>

6、创建工具类来获取SqlSession

package org.danni.utils;

import java.io.IOException;
import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class SqlSessionUtils {

private static SqlSessionFactory sqlSessionFactory;
private static SqlSession sqlSession;

public static SqlSessionFactory openSessionFactory() {
if (sqlSessionFactory == null) {
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
return sqlSessionFactory;
}

public static SqlSession openSession() {
if (sqlSession == null) {
sqlSession = openSessionFactory().openSession();
}
return sqlSession;
}
}

7、创建AdminsTest测试类来了解mybatis用法

AdminsTest：记得要提交事务

package com.danni.test;

import org.apache.ibatis.session.SqlSession;
import org.danni.utils.SqlSessionUtils;

import com.danni.model.dao.AdminsMapper;
import com.danni.model.entity.Admins;

public class AdminsTest {
// 增
public static void add() {
// 开启sqlSession
SqlSession sqlSession = SqlSessionUtils.openSession();

Admins admins = new Admins();
admins.setAdminname("小红");
admins.setAdminpwd("123");

// 法一：直接调用
Integer row = sqlSession.insert("com.danni.model.dao.AdminsMapper.insert", admins);
sqlSession.commit();

System.out.println(row);
}

// 增
public static void add1() {
// 开启sqlSession
SqlSession sqlSession = SqlSessionUtils.openSession();

Admins admins = new Admins();
admins.setAdminname("小白");
admins.setAdminpwd("123");

// 法二：采用接口代理的方式(然后就直接调用接口中相应的方法，他会去实现类也就对应的xml中找对应的方法)
AdminsMapper adminsDao = sqlSession.getMapper(AdminsMapper.class);
Integer row = adminsDao.insert(admins);
// 提交事务
sqlSession.commit();
System.out.println(row);
}

// update
public static void update() {
SqlSession sqlSession = SqlSessionUtils.openSession();

// 因为update，因此需要设置id，根据id进行更新
Admins admins = new Admins();
admins.setAdminname("呵呵");
admins.setAdminpwd("123");
admins.setAid(11);

AdminsMapper adminsDao = sqlSession.getMapper(AdminsMapper.class);
adminsDao.updateByPrimaryKey(admins);
// 提交事务
sqlSession.commit();
}

public static void main(String[] args) {
// add();
// add1();
update();
}
}

8、一对一关系

（1）修改Employee.java文件：

public class Employee implements Serializable{
private Integer eid;
private String ename;
private String esex;
private Department department;
//get和set方法不贴出来了，自己补全
}

（2）修改EmployeeMapper.xml文件：需要把sql语句中对应的对象中原来的did全部换成department.did

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.danni.model.dao.EmployeeMapper">

<resultMap id="BaseResultMap" type="com.danni.model.entity.Employee">
<id column="eid" jdbcType="INTEGER" property="eid" />
<result column="ename" jdbcType="VARCHAR" property="ename" />
<result column="esex" jdbcType="VARCHAR" property="esex" />

<!-- select：去department中根据id查询，column：表明关联的依据 -->
<association property="department" column="did" select="com.danni.model.dao.DepartmentMapper.selectByPrimaryKey"></association>
</resultMap>

<sql id="Base_Column_List">
eid, ename, esex, did
</sql>

<select id="selectByPrimaryKey" parameterType="java.lang.Integer" resultMap="BaseResultMap">
select
<include refid="Base_Column_List" />
from employee
where eid = #{eid,jdbcType=INTEGER}
</select>

<delete id="deleteByPrimaryKey" parameterType="java.lang.Integer">
delete from employee
where eid = #{eid,jdbcType=INTEGER}
</delete>
<insert id="insert" parameterType="com.danni.model.entity.Employee">
insert into employee (eid, ename, esex,
did)
values (#{eid,jdbcType=INTEGER}, #{ename,jdbcType=VARCHAR}, #{esex,jdbcType=VARCHAR},
#{department.did,jdbcType=INTEGER})
</insert>
<insert id="insertSelective" parameterType="com.danni.model.entity.Employee">
insert into employee
<trim prefix="(" suffix=")" suffixOverrides=",">
<if test="eid != null">
eid,
</if>
<if test="ename != null">
ename,
</if>
<if test="esex != null">
esex,
</if>
<if test="did != null">
did,
</if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides=",">
<if test="eid != null">
#{eid,jdbcType=INTEGER},
</if>
<if test="ename != null">
#{ename,jdbcType=VARCHAR},
</if>
<if test="esex != null">
#{esex,jdbcType=VARCHAR},
</if>
<if test="did != null">
#{department.did,jdbcType=INTEGER},
</if>
</trim>
</insert>
<update id="updateByPrimaryKeySelective" parameterType="com.danni.model.entity.Employee">
update employee
<set>
<if test="ename != null">
ename = #{ename,jdbcType=VARCHAR},
</if>
<if test="esex != null">
esex = #{esex,jdbcType=VARCHAR},
</if>
<if test="did != null">
did = #{department.did,jdbcType=INTEGER},
</if>
</set>
where eid = #{eid,jdbcType=INTEGER}
</update>
<update id="updateByPrimaryKey" parameterType="com.danni.model.entity.Employee">
update employee
set ename = #{ename,jdbcType=VARCHAR},
esex = #{esex,jdbcType=VARCHAR},
did = #{department.did,jdbcType=INTEGER}
where eid = #{eid,jdbcType=INTEGER}
</update>
</mapper>

（3）测试类EmpDepartTest：

public class EmpDepartTest {

// 查询职工，会通知查询出职工在的部门对象
public static void queryEmpByDid() {
SqlSession sqlSession = SqlSessionUtils.openSession();
EmployeeMapper employeeDao = sqlSession.getMapper(EmployeeMapper.class);
Employee employee = employeeDao.selectByPrimaryKey(10);
System.out.println(employee.getEname() + " " + employee.getDepartment().getDepartname());
}

public static void main(String[] args) {
queryEmpByDid();
}
}

9、多对一关系

一个部门对应多个员工。因此在部门中增加员工集合作为它的属性

（1）修改Department.java

public class Department implements Serializable{
private Integer did;
private String departname;
private List<Employee> empLists;
//get和set方法自己补，我就不贴出来了
}

（2）修改DepartmentMapper.xml的结果映射

<resultMap id="BaseResultMap" type="com.danni.model.entity.Department">
<id column="did" jdbcType="INTEGER" property="did" />
<result column="departname" jdbcType="VARCHAR" property="departname" />

<!-- 一对多关系:去员工中查询did为某个值的员工对象 -->
<collection property="empLists" column="did" select="com.danni.model.dao.EmployeeMapper.selectByDid"></collection>
</resultMap>

（2）员工中新增selectByDid方法

EmployeeMapper.java：先去接口中添加对应方法声明

EmployeeMapper.xml：增加对应的实现

<select id="selectByDid" parameterType="int" resultType="BaseResultMap">
select * from employee where did = #{did}
</select>

（3）编写测试类中对应方法

// 查询某个部门的全部员工(查询部门的时候同时会把属于这个部门的所欲员工集合查询出来，就达到了一对多的关系)
public static void queryDepartEmps() {
SqlSession sqlSession = SqlSessionUtils.openSession();
DepartmentMapper departmentMapper = sqlSession.getMapper(DepartmentMapper.class);
Department department = departmentMapper.selectByPrimaryKey(3);
System.out.println(department.getEmpLists().size());
}

public static void main(String[] args) {
// queryEmpByDid();
queryDepartEmps();
}

10、分页

（1）在EmployeeMapper.java接口中新增对应方法声明

List<Employee> queryByPage(Map<String, Integer> map);

（2）在EmployeeMapper.xml中新增实现方法

注意：这里我传递的是一个map集合，集合的键的名字必须和测试类中map中的见得名字要对应相等

<select id="queryByPage" parameterType="map" resultMap="BaseResultMap">
select * from employee limit #{startNum},#{pageSize}
</select>

（3）添加对应测试类

// 分页(把页码作为参数)
public static void queryByPage(Integer pageIndex) {
SqlSession sqlSession = SqlSessionUtils.openSession();
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);

Map<String, Integer> map = new HashMap<String, Integer>();
map.put("startNum", (pageIndex-1)*3);       //limit的第一个参数
map.put("pageSize", 3);                     //limit的第二个参数
List<Employee> empLists = employeeMapper.queryByPage(map);
System.out.println("");
}

public static void main(String[] args) {
// queryEmpByDid();
// queryDepartEmps();
queryByPage(2);
}

11、排序，$符号的使用

（1）首先在接口中定义方法

List<Employee> queryBySort(String name);

（2）在实现类中添加相应的实现方法

<!-- 注意：这里一定要使用value，他是默认的，不然就找不到 -->
<select id="queryBySort" parameterType="string" resultMap="BaseResultMap">
select * from employee order by ${value}
</select>

（3）添加对应测试类

// 排序
public static void queryBySort() {
SqlSession sqlSession = SqlSessionUtils.openSession();
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);

List<Employee> empLists = employeeMapper.queryBySort("ename");
System.out.println("");
}

public static void main(String[] args) {
// queryEmpByDid();
// queryDepartEmps();
// queryByPage(2);
queryBySort();
}

12、动态sql

<insert id="insertSelective" parameterType="com.danni.model.entity.Employee">
insert into employee
<trim prefix="(" suffix=")" suffixOverrides=",">
<if test="eid != null">
eid,
</if>
<if test="ename != null">
ename,
</if>
<if test="esex != null">
esex,
</if>
<if test="did != null">
did,
</if>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides=",">
<if test="eid != null">
#{eid,jdbcType=INTEGER},
</if>
<if test="ename != null">
#{ename,jdbcType=VARCHAR},
</if>
<if test="esex != null">
#{esex,jdbcType=VARCHAR},
</if>
<if test="did != null">
#{department.did,jdbcType=INTEGER},
</if>
</trim>
</insert>

update:

<update id="updateByPrimaryKeySelective" parameterType="com.danni.model.entity.Employee">
update employee
<set>
<if test="ename != null">
ename = #{ename,jdbcType=VARCHAR},
</if>
<if test="esex != null">
esex = #{esex,jdbcType=VARCHAR},
</if>
<if test="did != null">
did = #{department.did,jdbcType=INTEGER},
</if>
</set>
where eid = #{eid,jdbcType=INTEGER}
</update>