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URL、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>