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MyBatis接口代理方式实现Dao层 接口代理方式-实现规则 传统方式实现Dao层，我们既要写接口。还要写实现类。而MyBatis框架可以帮助我们省略写Dao层接口实现类的步骤。程序员只需要编写接口，由MyBatis框架根据接口的定义来创 1该接口的动态代理对象。 实现规则： 1.映射配置文件中的名称空间必须和Dao层接口的全类名相同 2.映射配置文件中的增删改查标签的id属性必须和Dao层接口的方法名相同 3.映射配置文件中的增删改查标签的paramrterType属性必须和Dao层接口方法的参数相同 4.映射配置文件中的增删改查标签的resultType属性必须和Dao层接口方法的返回值相同 接口代理方式-代码实现 1.删除mapper层接口的实现类 2.修改映射配置文件 3.修改service层接口的实现类，采用接口代理方式实现功能
删除mapper层接口的实现类
修改映射配置文件 package com.itheima.service.impl; import com.itheima.bean.Student; import com.itheima.mapper.StudentMapper; import com.itheima.service.StudentService; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.IOException; import java.io.InputStream; import java.util.List; /* 业务层实现类 */ public class StudentServiceImpl implements StudentService { @Override public List selectAll() { List list = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 list = mapper.selectAll(); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return list; } @Override public Student selectById(Integer id) { Student stu = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 stu = mapper.selectById(id); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return stu; } @Override public Integer insert(Student stu) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.insert(stu); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } @Override public Integer update(Student stu) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.update(stu); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } @Override public Integer delete(Integer id) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.delete(id); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } }修改service层接口的实现类，采用接口代理方式实现功能 接口代理方式-源码分析 分析动态代理对象如何生成的？ 通过动态代理开发的模式，我们只需要编写一个接口，不写实现类，我们通过getMapper()方法最终获取到 org.apache.ibatis.binding.MapperProxy代理对象，然后执行功能，而这个代理对象正是MyBatis使用了JDK的动态代理技术，帮助我们生成了代理实现类对象。从而可以进行相关持久化操作。 分析方法是如何执行的？ 动态代理的实现类对象再执行方法的时候最终调用了maperMethod.execute()方法，这个方法中通过switch语句根据操作类型来判断是新增，修改，删除，查询操作，最后一步回到了MMyBatis最原生的SqlSession方式来执行增删改查。 接口代理方式小结 接口代理方式可以让我们只编写接口即可，而实现类对象由MyBatis生成。 实现规则： 1.映射配置文件中的名称空间必须和Dao层接口的全类名相同 2.映射配置文件中的增删改查标签的id属性必须和Dao层接口的方法名相同 3.映射配置文件中的增删改查标签的paramrterType属性必须和Dao层接口方法的参数相同 4.映射配置文件中的增删改查标签的resultType属性必须和Dao层接口方法的返回值相同 获取动态代理对象 SqlSession功能类中的getMapper()方法 删除mapper中的实现类 ，保留接口 在StudentMapper.xml中修改 更改service包下 StudentServiceImpl文件 package com.itheima.service.impl; import com.itheima.bean.Student; import com.itheima.mapper.StudentMapper; import com.itheima.service.StudentService; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import java.io.IOException; import java.io.InputStream; import java.util.List; /* 业务层实现类 */ public class StudentServiceImpl implements StudentService { @Override public List selectAll() { List list = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 list = mapper.selectAll(); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return list; } @Override public Student selectById(Integer id) { Student stu = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 stu = mapper.selectById(id); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return stu; } @Override public Integer insert(Student stu) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.insert(stu); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } @Override public Integer update(Student stu) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.update(stu); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } @Override public Integer delete(Integer id) { Integer result = null; SqlSession sqlSession = null; InputStream is = null; try{ //1.加载核心配置文件 is = Resources.getResourceAsStream("MyBatisConfig.xml"); //2.获取SqlSession工厂对象 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); //3.通过工厂对象获取SqlSession对象 sqlSession = sqlSessionFactory.openSession(true); //4.获取StudentMapper接口的实现类对象 StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); // StudentMapper mapper = new StudentMapperImpl(); //5.通过实现类对象调用方法，接收结果 result = mapper.delete(id); } catch (Exception e) { } finally { //6.释放资源 if(sqlSession != null) { sqlSession.close(); } if(is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } //7.返回结果 return result; } }创建dynamic下测试类Test01 package com.itheima.dynamic; import com.itheima.bean.Student; import com.itheima.mapper.StudentMapper; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; import org.junit.Test; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.List; public class Test01 { @Test public void selectCondition() throws Exception { InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); SqlSession sqlSession = sqlSessionFactory.openSession(true); StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); Student stu=new Student(); stu.setId(2); stu.setName("李四"); //stu.setAge(23); List list = mapper.selectCondition(stu); for (Student student:list){ System.out.println(student); } sqlSession.close(); is.close(); } @Test public void selectByIds() throws Exception { InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml"); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is); SqlSession sqlSession = sqlSessionFactory.openSession(true); StudentMapper mapper = sqlSession.getMapper(StudentMapper.class); List ids=new ArrayList(); ids.add(1); ids.add(2); List list = mapper.selectByIds(ids); for (Student student:list){ System.out.println(student); } sqlSession.close(); is.close(); } }
MyBatis映射配置文件-----动态sql 动态SQL介绍 MyBatis映射配置文件中，前面我们的SQL都是比较简单的，有些时候业务逻辑复杂时，我们的SQL就时动态变化的，此时在前面学习的SQL就不能满足要求了。 多条件查询 id：3 name：王五 age：25 select * from Student where id=#{id} and name=#{name} and age=#{age}id：3 name：王五 select * from Student where id=#{id} and name=#{name}动态sql标签 :条件标签。如果有动态条件，则使用该标签代替where关键字。 :条件判断标签 查询条件拼接 :循环遍历标签。适用于多个参数或者的关系。 获取参数属性： collection：参数容器类型，（list-集合，array-数组）。 open：开始的sql语句 close：结束额sql语句 item：参数变量名 separator：分隔符 Sql片段抽取 我们可以将一些重复的SQL语句进行抽取，以达到复用的效果 : 抽取SQL语句标签 抽取的SQL语句 :引入SQL片段标签
StudentMapper.xml Select * FROM Student where id = #{id} Insert into Student values(#{id},#{name},#{age}) update Student set name =#{name},age=#{age} where id=#{id} delete from Student where id=#{id} id=#{id} and name=#{name} and age=#{age} #{id}动态SQL小结 动态SQL指的就是SQL语句可以根据条件或者参数的不同进行动态的变化 :条件标签 :里面有个test标签可以帮我们进行判断 :循环遍历的标签 collection="list" open="id in (" close=")" item="id" separator="," :抽取SQL片段的标签 :引入SQL片段的标签
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