最近学完mybytis，记录一个简单的工程，从配置环境开始，以便日后查阅

导入依赖

这里是在父工程中（即创建的第一个maven项目，删除src目录，即自动变为父工程，后面的module会自动继承父工程）

mysql驱动5.1.47mybatis3.5.2junit4.1.2log4j日志lombok：偷懒用，引用注解后可省去getter，setter等方法build中包含的是为了确保读到java文件夹下的xml和properties文件，resources下的文件可以被自动识别并读取 <?xml version="1.0" encoding="UTF-8"?> <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> <!--父工程--> <groupId>com.fanjh</groupId> <artifactId>Mabatis-Study</artifactId> <packaging>pom</packaging> <version>1.0-SNAPSHOT</version> <modules> <module>mybatis-01</module> <module>mybatis-02</module> <module>mybatis-03</module> <module>mybatis-04</module> <module>mybatis-05</module> <module>mybatis-07</module> <module>mybatis-08</module> <module>mybatis-09</module> </modules> <dependencies> <!--mysql驱动--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.47</version> </dependency> <!--mybatis--> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.2</version> </dependency> <!--junit--> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.12</version> <scope>provided</scope> </dependency> </dependencies> <build> <resources> <resource> <directory>src/main/java</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>true</filtering> </resource> </resources> </build> </project>

环境配置

mybatis-config.xml

属性（properties）：通过properties来实现引用配置文件设置（settings）：使用标准日志别名（typeAliases)：所有的pojo文件夹下的类都可以使用默认别名默认事物管理器：JDBC连接池：POOLED映射器（mappers）：所有的mapper文件都需要注册 <?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> <properties resource="db.properties"> </properties> <settings> <setting name="logImpl" value="STDOUT_LOGGING"/> </settings> <typeAliases> <package name="com.fanjh.pojo"/> </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/fanjh/dao/StudentMapper.xml"/> <mapper resource="com/fanjh/dao/TeacherMapper.xml"/> </mappers> </configuration>

db.properties

这里注意useSSL设置为false

driver=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8 username=root password=xxxxxx

以上都放在resources文件夹下，注意文件夹标记为ResourcesRoot。

编写mybatis工具类

一般都放在utils文件夹下

public class MybatisUtils { private static SqlSessionFactory sqlSessionFactory; static{ try { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(); } }

编写实体类

实体类就根据数据库中的字段名和字段类型进行编写

@Data public class Teacher { private int id; private String name; private List<Student> students; } @Data public class Student { private int id; private String name; private int tid; }

编写Mapper接口

mapper接口中定义了对应的实体类的方法，名字上尽量取到和实体类同名，这里是TeacherMapper和StudentMapper。

public interface TeacherMapper { //获取指定老师的信息及其所有学生的信息 List<Teacher> getTeacher(@Param("tid") int id); }

编写Mapper.xml配置文件

配置文件也是尽量和接口同名，这里是TeacherMapper.xml和StudentMapper.xml，namespace关联到对应的接口

注意！mapper.xml一定要在核心配置文件中注册

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.fanjh.dao.TeacherMapper"> <!--按结果嵌套查询--> <select id="getTeacher" resultMap="teacherstudent"> select t.id tid, t.name tname, s.id sid, s.name from mybatis.teacher t join mybatis.student s on t.id = s.tid where t.id = #{tid} </select> <resultMap id="teacherstudent" type="teacher"> <result property="id" column="tid"/> <result property="name" column="tname"/> <collection property="students" ofType="student"> <result property="id" column="sid"/> <result property="name" column="sname"/> </collection> </resultMap> </mapper>

编写测试类

一切就绪后就可以编写测试类了，测试类放在src.test文件夹下，尽量和接口及对应xml文件在同名文件夹下。

public class MyTest { @Test public void test(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class); List<Teacher> teachers = mapper.getTeacher(1); for (Teacher teacher : teachers) { System.out.println(teacher); } sqlSession.close(); } }

首尾的步骤是固定的，得到mapper后就可以使用接口中定义的方法，注意对于CRUD操作，一定要记得提交，否则不会生效：sqlsession.commit()