mybatis第一篇

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mybatis第一篇

什么是mybatis，mybatis有什么特点

在JDBC和hibernate中间找到一个平衡点，结合它们的优点，摒弃它们的缺点， 这就是myBatis，现今myBatis被广泛的企业所采用。

MyBatis 本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code，并且改名为MyBatis 。2013年11月迁移到Github。

iBATIS一词来源于“internet”和“abatis”的组合，是一个基于Java的持久层框架。iBATIS提供的持久层框架包括SQL Maps和Data Access Objects（DAO）

jdbc/dbutils/springdao，hibernate/springorm，mybaits同属于ORM解决方案之一

mybatis快速入门

  1. 创建一个mybatis-day01这么一个javaweb工程或java工程

  2. 导入mybatis和mysql/oracle的jar包到/WEB-INF/lib目录下

  3. 创建students.sql表

--mysql语法
create table students(
   id  int(5) primary key,
   name varchar(10),
   sal double(8,2)
);
--oracle语法
create table students(
   id  number(5) primary key,
   name varchar2(10),
   sal number(8,2)
);
  1. 创建Student.java
/**
 * 学生
 * @author csx
 */
public class Student 
	private Integer id;
	private String name;
	private Double sal;
	public Student()
	public Integer getId() 
		return id;
	
	public void setId(Integer id) 
		this.id = id;
	
	public String getName() 
		return name;
	
	public void setName(String name) 
		this.name = name;
	
	public Double getSal() 
		return sal;
	
	public void setSal(Double sal) 
		this.sal = sal;
  1. 在entity目录下创建StudentMapper.xml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">

<mapper namespace="mynamespace">
	<insert id="add1">
		insert into students(id,name,sal) values(1,'哈哈',7000)
	</insert>
	<insert id="add2" parameterType="cn.csx.javaee.mybatis.app05.Student">
		insert into students(id,name,sal) values(#id,#name,#sal)
	</insert>
</mapper>
  1. 在src目录下创建mybatis.xml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>
	<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://127.0.0.1:3306/mybatis"/>	
				<property name="username" value="root"/>	
				<property name="password" value="root"/>	
			</dataSource>
		</environment>	
	</environments>
	<mappers>
		<mapper resource="cn/csx/javaee/mybatis/app05/StudentMapper.xml"/>
	</mappers>
</configuration>
  1. 在util目录下创建MyBatisUtil.java类，并测试与数据库是否能连接
/**
 * MyBatis工具类
 * @author csx
 */
public class MyBatisUtil 
	private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();
	private static SqlSessionFactory sqlSessionFactory;
	static
		try 
			Reader reader = Resources.getResourceAsReader("mybatis.xml");
			sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
		 catch (IOException e) 
			e.printStackTrace();
			throw new RuntimeException(e);
		
	
	private MyBatisUtil()
	public static SqlSession getSqlSession()
		SqlSession sqlSession = threadLocal.get();
		if(sqlSession == null)
			sqlSession = sqlSessionFactory.openSession();
			threadLocal.set(sqlSession);
		
		return sqlSession;
	
	public static void closeSqlSession()
		SqlSession sqlSession = threadLocal.get();
		if(sqlSession != null)
			sqlSession.close();
			threadLocal.remove();
		
	
	public static void main(String[] args) 
		Connection conn = MyBatisUtil.getSqlSession().getConnection();
		System.out.println(conn!=null?"连接成功":"连接失败");
  1. 在dao目录下创建StudentDao.java类并测试
/**
 * 持久层
 * @author AdminTC
 */
public class StudentDao 
	/**
	 * 增加学生（无参）
	 */
	public void add1() throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			sqlSession.insert("mynamespace.add1");
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
		
		MyBatisUtil.closeSqlSession();
	
	/**
	 * 增加学生（有参）
	 */
	public void add2(Student student) throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			sqlSession.insert("mynamespace.add2",student);
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
		
		MyBatisUtil.closeSqlSession();
	
	public static void main(String[] args) throws Exception
		StudentDao dao = new StudentDao();
		dao.add1();
		dao.add2(new Student(2,"呵呵",8000D));

mybatis工作流程

  1. 通过Reader对象读取src目录下的mybatis.xml配置文件(该文本的位置和名字可任意)
  2. 通过SqlSessionFactoryBuilder对象创建SqlSessionFactory对象
  3. 从当前线程中获取SqlSession对象
  4. 事务开始，在mybatis中默认
  5. 通过SqlSession对象读取StudentMapper.xml映射文件中的操作编号，从而读取sql语句
  6. 事务提交，必写
  7. 关闭SqlSession对象，并且分开当前线程与SqlSession对象，让GC尽早回收

mybatis配置文件祥解（mybatis.xml）

以下是mybatis.xml文件，提倡放在src目录下，文件名任意

<?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>
	<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://127.0.0.1:3306/mybatis"/>	
				<property name="username" value="root"/>	
				<property name="password" value="root"/>	
			</dataSource>
		</environment>	
	</environments>
	<mappers>
		<mapper resource="cn/csx/javaee/mybatis/app05/StudentMapper.xml"/>
	</mappers>
</configuration>

mybatis映射文件祥解(StudentMapper.xml)

以下是StudentMapper.xml文件，提倡放在与实体同目录下，文件名任意

<?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="mynamespace">
	<insert id="add1">
		insert into students(id,name,sal) values(1,'哈哈',7000)
	</insert>
	<insert id="add2" parameterType="cn.csx.javaee.mybatis.app05.Student">
		insert into students(id,name,sal) values(#id,#name,#sal)
	</insert>
</mapper>

MybatisUtil工具类的作用

  1. 在静态初始化块中加载mybatis配置文件和StudentMapper.xml文件一次
  2. 使用ThreadLocal对象让当前线程与SqlSession对象绑定在一起
  3. 获取当前线程中的SqlSession对象，如果没有的话，从SqlSessionFactory对象中获取SqlSession对象
  4. 获取当前线程中的SqlSession对象，再将其关闭，释放其占用的资源
/**
 * MyBatis工具类
 * @author AdminTC
 */
public class MyBatisUtil 
	private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();
	private static SqlSessionFactory sqlSessionFactory;
	static
		try 
			Reader reader = Resources.getResourceAsReader("mybatis.xml");
			sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
		 catch (IOException e) 
			e.printStackTrace();
			throw new RuntimeException(e);
		
	
	private MyBatisUtil()
	public static SqlSession getSqlSession()
		SqlSession sqlSession = threadLocal.get();
		if(sqlSession == null)
			sqlSession = sqlSessionFactory.openSession();
			threadLocal.set(sqlSession);
		
		return sqlSession;
	
	public static void closeSqlSession()
		SqlSession sqlSession = threadLocal.get();
		if(sqlSession != null)
			sqlSession.close();
			threadLocal.remove();
		
	
	public static void main(String[] args) 
		Connection conn = MyBatisUtil.getSqlSession().getConnection();
		System.out.println(conn!=null?"连接成功":"连接失败");

基于MybatisUtil工具类，完成CURD操作

StudentDao.java

/**
 * 持久层
 * @author AdminTC
 */
public class StudentDao 
	/**
	 * 增加学生
	 */
	public void add(Student student) throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			sqlSession.insert("mynamespace.add",student);
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
			MyBatisUtil.closeSqlSession();
		
	
	/**
	 * 修改学生
	 */
	public void update(Student student) throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			sqlSession.update("mynamespace.update",student);
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
			MyBatisUtil.closeSqlSession();
		
	
	/**
	 * 查询单个学生
	 */
	public Student findById(int id) throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			Student student = sqlSession.selectOne("mynamespace.findById",id);
			return student;
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
			MyBatisUtil.closeSqlSession();
		
	
	/**
	 * 查询多个学生
	 */
	public List<Student> findAll() throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			return sqlSession.selectList("mynamespace.findAll");
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
			MyBatisUtil.closeSqlSession();
		
	
	/**
	 * 删除学生
	 */
	public void delete(Student student) throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			sqlSession.delete("mynamespace.delete",student);
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
			MyBatisUtil.closeSqlSession();
  1. StudentMapper.xml
<?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="mynamespace">
	<insert id="add" parameterType="cn.csx.javaee.mybatis.app09.Student">
		insert into students(id,name,sal) values(#id,#name,#sal)
	</insert>
	<update id="update" parameterType="cn.csx.javaee.mybatis.app09.Student">
		update students set name=#name,sal=#sal where id=#id
	</update>
	<select id="findById" parameterType="int" resultType="cn.csx.javaee.mybatis.app09.Student">
		select id,name,sal from students where id=#anything
	</select>
	<select id="findAll" resultType="cn.csx.javaee.mybatis.app09.Student">
		select id,name,sal from students
	</select>
	<delete id="delete" parameterType="cn.csx.javaee.mybatis.app09.Student">
		delete from students where id=#id
	</delete>
</mapper>

分页查询

StudentDao.java

/**
 * 持久层
 * @author csx
 */
public class StudentDao 
	/**
	 * 增加学生
	 */
	public void add(Student student) throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			sqlSession.insert("mynamespace.add",student);
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
			MyBatisUtil.closeSqlSession();
		
	
	/**
	 * 无条件分页查询学生
	 */
	public List<Student> findAllWithFy(int start,int size) throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			Map<String,Integer> map = new LinkedHashMap<String,Integer>();
			map.put("pstart",start);
			map.put("psize",size);
			return sqlSession.selectList("mynamespace.findAllWithFy",map);
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
			MyBatisUtil.closeSqlSession();
		
	
	/**
	 * 有条件分页查询学生
	 */
	public List<Student> findAllByNameWithFy(String name,int start,int size) throws Exception
		SqlSession sqlSession = MyBatisUtil.getSqlSession();
		try
			Map<String,Object> map = new LinkedHashMap<String,Object>();
			map.put("pname","%"+name+"%");
			map.put("pstart",start);
			map.put("psize",size);
			return sqlSession.selectList("mynamespace.findAllByNameWithFy",map);
		catch(Exception e)
			e.printStackTrace();
			sqlSession.rollback();
			throw e;
		finally
			sqlSession.commit();
			MyBatisUtil.closeSqlSession();
		
	
	public static void main(String[] args) throws Exception
		StudentDao dao = new StudentDao();
		System.out.println("-----------Page1");
		for(Student s:dao.findAllByNameWithFy("哈",0,3))
			System.out.println(s.getId()+":"+s.getName()+":"+s.getSal());
		
		System.out.println("-----------Page2");
		for(Student s:dao.findAllByNameWithFy("哈",3,3))
			System.out.println(s.getId()+":"+s.getName()+":"+s.getSal());
		
		System.out.println("-----------Page3");
		for(Student s:dao.findAllByNameWithFy("哈",6,3))
			System.out.println(s.getId()+":"+s.getName()+":"+s.getSal());
		
		System.out.println("-----------Page4");
		for(Student s:dao.findAllByNameWithFy("哈",9,3))
			System.out.MyBatis框架之第一篇


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