依赖如下
<dependencies> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.15</version> </dependency> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.1</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.11</version> <scope>test</scope> </dependency> </dependencies>
MyBatis应用是以SqlSessionFactory为中心的,实例可以通过SqlSessionFactoryBuilder获得.
其中SqlSessionFactory是工厂接口,任务用于创建SqlSession
配置文件将会解析配置XML文件在Configuration类对象中.
在resource文件下新建mybatis-config.xml文件
配置文件内容如下
<?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> <!-- 定义别名 --> <typeAliases> <typeAlias type="com.ming.Role" alias="role"/> </typeAliases> <!-- 定义数据库信息 --> <environments default="development"> <environment id="development"> <!-- jdbc事物管理 --> <transactionManager type="JDBC"></transactionManager> <!-- 数据库链接信息 --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.cj.jdbc.Driver"/> <property name="url" value="jdbc:mysql://47.94.95.84:32786/mybatis"/> <property name="username" value="mybatis"/> <property name="password" value="ABCcba20170607"/> </dataSource> </environment> </environments> </configuration>
新建类
package com.ming; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.IOException; import java.io.InputStream; public class Role { public String getSqlSessionFactory(){ String resource = "mybatis-config.xml"; try {// 获得输入流 InputStream inputStream; inputStream = Resources.getResourceAsStream(resource); // 获得SqlSessionFactory工厂 SqlSessionFactory sqlSessionFactory = null; sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); }catch (IOException e){ e.printStackTrace(); } return null; } }
最后新建测试类
package com.ming; import org.junit.After; import org.junit.Before; import org.junit.Test; public class RoleTest { private Role role = null; @Before public void setUp() throws Exception { this.role = new Role(); } @After public void tearDown() throws Exception { } @Test public void getSqlSessionFactory() { role.getSqlSessionFactory(); } }
此时的目录结构
public SqlSessionFactory getSqlSessionFactory1(){ // 创建数据库连接池 PooledDataSource dataSource = new PooledDataSource(); dataSource.setDriver("com.mysql.cj.jdbc.Driver"); dataSource.setUrl("jdbc:mysql://47.94.95.84:32786/mybatis"); dataSource.setUsername("mybatis"); dataSource.setPassword("ABCcba20170607"); // 构建数据库事物 TransactionFactory transactionFactory = new JdbcTransactionFactory(); // 创建数据库环境 Environment environment = new Environment("development", transactionFactory, dataSource); // 构建Configuration对象 Configuration configuration = new Configuration(environment); // 注册上下文别名 configuration.getTypeAliasRegistry().registerAlias("role", Role.class); // 创建映射器 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration); return sqlSessionFactory; }
书写测试用例如下
package com.ming; import org.junit.After; import org.junit.Before; import org.junit.Test; public class RoleTest { private Role role = null; @Before public void setUp() throws Exception { this.role = new Role(); } @After public void tearDown() throws Exception { } @Test public void getSqlSessionFactory() { role.getSqlSessionFactory(); } @Test public void getSqlSessionFactory1() { role.getSqlSessionFactory1(); } }
SqlSession属于门面,通过SqlSession可以获得需要的什么信息
SqlSession sqlSession = null; try{ // 创建一个sqlsession会话 sqlSession = sqlSessionFactory.openSession(); sqlSession.commit(); }catch (Exception e){ // 输出错误信息 System.out.println(e.getMessage()); // 进行事物操作,回滚数据库数据 sqlSession.rollback(); }finally { // 进行资源关闭 if(sqlSession != null){ sqlSession.close(); } }
SqlSession作用,获取映射器,通过命名信息执行sql结果
映射器由java和xml文件共同组成,作用
定义参数类型
描述缓存
描述sql
定义查询结果和POJO映射关系
先给出java接口
package com.ming; public interface RoleMapper { public Role getRole(Long id); }
根据给定的id获取角色对象
给出映射文件,然后在生成的时候会根据接口实现类,生成对象.
先编写POJO
package com.ming; // POJO public class Role { private int id; private String roleName; private String note; public void setId(int id) { this.id = id; } public void setRoleName(String roleName) { this.roleName = roleName; } public void setNote(String note) { this.note = note; } public int getId() { return id; } public String getRoleName() { return roleName; } public String getNote() { return note; } }
在编写映射配置文件
<?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"> <!-- 定义接口类 --> <mapper namespace="com.ming.RoleMapper"> <!-- 定义的接口方法为getRole 类型参数为long 返回的结果为role 即之前定义在xml文件中定义的vo别名 --> <select id="getRole" parameterType="int" resultType="role"> <!-- 定义sql语句--> SELECT id, role_name as roleName, note FROM t_role WHERE id = #{id} </select> </mapper>
最后编写mybatis,添加映射器配置文件
<?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> <!-- 定义别名 --> <typeAliases> <typeAlias type="com.ming.Role" alias="role"/> </typeAliases> <!-- 定义数据库信息 --> <environments default="development"> <environment id="development"> <!-- jdbc事物管理 --> <transactionManager type="JDBC"></transactionManager> <!-- 数据库链接信息 --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.cj.jdbc.Driver"/> <property name="url" value="jdbc:mysql://47.94.95.84:32786/mybatis"/> <property name="username" value="mybatis"/> <property name="password" value="ABCcba20170607"/> </dataSource> </environment> </environments> <!-- 定义映射器 --> <mappers> <mapper resource="RoleMapper.xml"></mapper> </mappers> </configuration>
最后再编写执行sql的类
package com.ming; import org.apache.ibatis.datasource.pooled.PooledDataSource; import org.apache.ibatis.io.Resources; import org.apache.ibatis.mapping.Environment; import org.apache.ibatis.session.Configuration; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.apache.ibatis.transaction.TransactionFactory; import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory; import java.io.IOException; import java.io.InputStream; public class MyBatis { public String getSqlSessionFactory(){ String resource = "mybatis-config.xml"; SqlSessionFactory sqlSessionFactory = null; try {// 获得输入流 InputStream inputStream; inputStream = Resources.getResourceAsStream(resource); // 获得SqlSessionFactory工厂 sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); }catch (IOException e){ e.printStackTrace(); } SqlSession sqlSession = null; try{ // 创建一个sqlsession会话 sqlSession = sqlSessionFactory.openSession(); // 获得映射器 // 接口传入映射器中 RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class); // 执行方法 Role role = roleMapper.getRole(0); System.out.println(role.getRoleName()); // 刷新语句并提交链接 sqlSession.commit(); }catch (Exception e){ // 输出错误信息 System.out.println(e.getMessage()); // 进行事物操作,回滚数据库数据 sqlSession.rollback(); }finally { // 进行资源关闭 if(sqlSession != null){ sqlSession.close(); } } return null; } public SqlSessionFactory getSqlSessionFactory1(){ // 创建数据库连接池 PooledDataSource dataSource = new PooledDataSource(); dataSource.setDriver("com.mysql.cj.jdbc.Driver"); dataSource.setUrl("jdbc:mysql://47.94.95.84:32786/mybatis"); dataSource.setUsername("mybatis"); dataSource.setPassword("ABCcba20170607"); // 构建数据库事物 TransactionFactory transactionFactory = new JdbcTransactionFactory(); // 创建数据库环境 Environment environment = new Environment("development", transactionFactory, dataSource); // 构建Configuration对象 Configuration configuration = new Configuration(environment); // 注册上下文别名 configuration.getTypeAliasRegistry().registerAlias("role", MyBatis.class); // 创建映射器 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration); return sqlSessionFactory; } }
最后编写测试类
package com.ming; import org.junit.After; import org.junit.Before; import org.junit.Test; public class MyBatisTest { private MyBatis myBatis = null; @Before public void setUp() throws Exception { this.myBatis = new MyBatis(); } @After public void tearDown() throws Exception { } @Test public void getSqlSessionFactory() { myBatis.getSqlSessionFactory(); } @Test public void getSqlSessionFactory1() { myBatis.getSqlSessionFactory1(); } }
执行单元测试
结果如下
即完成了MyBatis的一次查询
定义接口
package com.ming; import org.apache.ibatis.annotations.Select; public interface Role1 { @Select (value="SELECT id, role_name as roleName, note FROM t_role WHERE id = #{id}") public Role getRole(int id); }
其是利用xml或者java编码构建SqlSessionFactory 可以构建多个SessionFactory 作用 构建器
根据构建器获得sqlSessionFactory
创建SqlSession 一个SqlSession相当于JDBC的Connection对象
此为单例管理
每创建一个SqlSession就会创建一个数据库连接
此为一个会话,相当于一个Connection连接 线程不安全
生命周期为一个应用的请求和操作,可以执行多条sql