Mybatis简单应用
Mybatis的核心组件：
- SqlSeeeionFactoryBuilder (构建器)：它会根据配置或者代码来生成SqlSessionFactory,采用的是分布构建的Builder模式；
- SqlSessionFactory:依靠它来生成SqlSession,使用的是工厂模式。
- SqlSession（会话）发送SQL执行并返回结果，也可以获取Mapper接口。
- SQL Mapper(映射器)： 由一个java接口和XML文件（或注解）构成，需要给出SQL的映射规则。它负责发送SQL去执行返回结果。
1.使用XML：mybatis-config.xml创建SqlSessionFactory的配置；
<?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>
<typeAliases><!-- 别名 -->
<typeAlias alias="role" type="com.learn.ssm.chapter3.pojo.Role"/>
</typeAliases>
<!-- 数据库环境 -->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/ssm"/>
<property name="username" value="root"/>
<property name="password" value="admin123"/>
</dataSource>
</environment>
</environments>
<!-- 映射文件 -->
<mappers>
<mapper resource="com/learn/ssm/chapter3/mapper/RoleMapper.xml"/>
<mapper class="com.learn.ssm.chapter3.mapper.RoleMapper2"/>
</mappers>
</configuration>
1.1 使用代码或xml创建SqlSessionFactory
package com.learn.ssm.chapter3.utils; import java.io.IOException; import java.io.InputStream; 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 com.learn.ssm.chapter3.mapper.RoleMapper; import com.learn.ssm.chapter3.mapper.RoleMapper2; import com.learn.ssm.chapter3.pojo.Role; public class SqlSessionFactoryUtils { private final static Class<SqlSessionFactoryUtils> LOCK = SqlSessionFactoryUtils.class; private static SqlSessionFactory sqlSessionFactory = null; private SqlSessionFactoryUtils() { } public static SqlSessionFactory getSqlSessionFactory() { synchronized (LOCK) { if (sqlSessionFactory != null) { return sqlSessionFactory; } String resource = "mybatis-config.xml"; InputStream inputStream; try { inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); return null; } return sqlSessionFactory; } } //代码生成SqlSessionFactory public static SqlSessionFactory getSqlSessionFactory2() { synchronized (LOCK) { //数据库连接池信息 PooledDataSource dataSource = new PooledDataSource(); dataSource.setDriver("com.mysql.jdbc.Driver"); dataSource.setUsername("root"); dataSource.setPassword("admin123"); dataSource.setUrl("jdbc:mysql://localhost:3306/ssm"); dataSource.setDefaultAutoCommit(false); //采用MyBatis的JDBC事务方式 TransactionFactory transactionFactory = new JdbcTransactionFactory(); Environment environment = new Environment("development", transactionFactory, dataSource); //创建Configuration对象 Configuration configuration = new Configuration(environment); //注册一个MyBatis上下文别名 configuration.getTypeAliasRegistry().registerAlias("role", Role.class); //加入一个映射器 configuration.addMapper(RoleMapper.class); configuration.addMapper(RoleMapper2.class); //使用SqlSessionFactoryBuilder构建SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration); return sqlSessionFactory; } } public static SqlSession openSqlSession() { if (sqlSessionFactory == null) { getSqlSessionFactory(); } return sqlSessionFactory.openSession(); } }
2. 映射器，由一个java接口和XML文件（或注解）构成
首先定义一个POJO
package com.learn.ssm.chapter3.pojo; public class Role { private Long id; private String roleName; private String note; /** setter and getter **/ public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getRoleName() { return roleName; } public void setRoleName(String roleName) { this.roleName = roleName; } public String getNote() { return note; } public void setNote(String note) { this.note = note; } }
2.1， 接口和XML实现映射
映射器接口：
public interface RoleMapper { public int insertRole(Role role); public int deleteRole(Long id); public int updateRole(Role role); public Role getRole(Long id); public List<Role> findRoles(String roleName); }
在XML创建SqlSession中有这样代码
<mapper resource="com/learn/ssm/chapter3/mapper/RoleMapper.xml"/>
引入XML（RoleMapper.xml）创建映射器（insert/select/update/delete）代表增/查/改/删
id 代表RoleMapper中方法名字
parameterType代表传入参数类型
resultType代表返回值 "role"是别名，代表<typeAlias alias="role" type="com.learn.ssm.chapter3.pojo.Role"/>
<?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.learn.ssm.chapter3.mapper.RoleMapper">
<insert id="insertRole" parameterType="role">
insert into t_role(role_name, note) values(#{roleName}, #{note})
</insert>
<delete id="deleteRole" parameterType="long">
delete from t_role where id= #{id}
</delete>
<update id="updateRole" parameterType="role">
update t_role set role_name = #{roleName}, note = #{note} where id= #{id}
</update>
<select id="getRole" parameterType="long" resultType="role">
select id,
role_name as roleName, note from t_role where id = #{id}
</select>
<select id="findRoles" parameterType="string" resultType="role">
select id, role_name as roleName, note from t_role
where role_name like concat('%', #{roleName}, '%')
</select>
</mapper>
2.2注解实现映射器
XML中引入Mapper:
<mapper class="com.learn.ssm.chapter3.mapper.RoleMapper2"/>
public interface RoleMapper2 { @Select("select id, role_name as roleName, note from t_role where id=#{id}") public Role getRole(Long id); @Insert("insert into t_role(role_name,note) values(#{roleName},#{note})") public void insertRole(Role role); }
注解不易于维护
3. 测试：
public class Chapter3Main {
public static void main(String[] args) {
testRoleMapper();
testRoleMapper2();
}
//xml 测试
private static void testRoleMapper() {
Logger log = Logger.getLogger(Chapter3Main.class);
SqlSession sqlSession = null;
try {
sqlSession = SqlSessionFactoryUtils.openSqlSession();
RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
Role role = roleMapper.getRole(1L);
Role r1 = new Role();
r1.setRoleName("testRole name");
r1.setNote("note...");
roleMapper.insertRole(r1);
sqlSession.commit();
log.info(role.getRoleName());
}
catch(Exception ex)
{
sqlSession.rollback();
}
finally {
if (sqlSession != null) {
sqlSession.close();
}
}
}
//注解SQL测试
private static void testRoleMapper2() {
Logger log = Logger.getLogger(Chapter3Main.class);
SqlSession sqlSession = null;
try {
sqlSession = SqlSessionFactoryUtils.openSqlSession();
RoleMapper2 roleMapper2 = sqlSession.getMapper(RoleMapper2.class);
Role role = roleMapper2.getRole(1L);
Role r1 = new Role();
r1.setRoleName("testRole name map2");
r1.setNote("note...");
roleMapper2.insertRole(r1);
sqlSession.commit();
log.info(role.getRoleName());
}
catch(Exception ex)
{
sqlSession.rollback();
}
finally {
if (sqlSession != null) {
sqlSession.close();
}
}
}
}
