参考文献:

原始dao方式

需要写dao接口和dao实现类。

• 创建dao接口：UserDao.java

package cn.itcast.mybatis.dao;import cn.itcast.mybatis.po.Employee;public interface UserDao {    public Employee findUserById(int id) throws Exception;    public void insertUser(Employee employee) throws Exception;    public void deleteUser(int id) throws Exception;}

• 创建dao实现类：UserDaoImpl.java

package cn.itcast.mybatis.dao;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import cn.itcast.mybatis.po.Employee;public class UserDaoImpl implements UserDao{    private SqlSessionFactory sqlSessionFactory;    public  UserDaoImpl(SqlSessionFactory sqlSessionFactory) {        this.sqlSessionFactory = sqlSessionFactory;    }    @Override    public Employee findUserById(int id) throws Exception {        SqlSession sqlSession =sqlSessionFactory.openSession();        Employee employee = sqlSession.selectOne("test.findUserById",id);        sqlSession.close();        return employee;    }    @Override    public void insertUser(Employee employee) throws Exception {        SqlSession sqlSession =sqlSessionFactory.openSession();        sqlSession.insert("test.insertUser",employee);        sqlSession.commit();        sqlSession.close();     }    @Override    public void deleteUser(int id) throws Exception {        SqlSession sqlSession =sqlSessionFactory.openSession();        sqlSession.delete("test.deleteUser",id);        sqlSession.commit();        sqlSession.close();     }}

• 测试方法：

package cn.itcast.mybatis.dao;import static org.junit.Assert.*;import java.io.InputStream;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import org.junit.Before;import org.junit.Test;import cn.itcast.mybatis.po.Employee;public class UserDaoImplTest {    private SqlSessionFactory sqlSessionFactory;    @Before    public void setUp() throws Exception{        String resource="SqlMapConfig.xml";        InputStream inputStream= Resources.getResourceAsStream(resource);        sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);    }    @Test    public void test() throws Exception {        UserDao userDao = new UserDaoImpl(sqlSessionFactory);        Employee employee = userDao.findUserById(3);        System.out.println(employee);    }}

缺点：

接口实现类方法中存在大量模板方法，设想能否将这些代码提取出来。

另外调用SqlSession方法时，将Statement的id硬编码了。

调用SqlSession方法时，传入的变量，由于SqlSession方法使用泛型，即使变量类型传入错误，在编译阶段也不报错，不利于开发。

mapper代理方法

• xml映射文件 (UserMapper.xml)
  ①在mapper.xml中namespace等于mapper接口地址
  ②mapper.java接口中的方法名和mapper.xml中的Statement的id一致
  ③mapper.java接口中的方法输入参数类型和mapper.xml中Statement的parameterType指定类型一致
  ④mapper.java接口中的方法返回值类型和mapper.xml中Statement的resultType指定的类型一致

          
               select id,username,sex,address from users where id=#{id};     
     

• mapper接口，相当于dao接口(UserMapper.java)

package cn.itcast.mybatis.mapper;import cn.itcast.mybatis.po.Employee;public interface UserMapper {    public Employee findUserById(int id) throws Exception;        public java.util.List
     
       findUserByName(String name) throws Exception;    public void insertUser(Employee employee ) throws Exception;    public void deleteUser(int id) throws Exception;}
     

• 还需在SqlMapConfig.xml加载映射文件

• 测试文件

package cn.itcast.mybatis.mapper;import static org.junit.Assert.*;import java.io.InputStream;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.Before;import org.junit.Test;import cn.itcast.mybatis.po.Employee;public class UserMapperTest {private SqlSessionFactory sqlSessionFactory;    @Before    public void setUp() throws Exception{        String resource="SqlMapConfig.xml";        InputStream inputStream= Resources.getResourceAsStream(resource);        sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);    }    @Test    public void test() throws Exception {        SqlSession sqlSession =sqlSessionFactory.openSession();        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);        Employee employee =userMapper.findUserById(2);        System.out.println(employee);    }        @Test    public void test1() throws Exception {        SqlSession sqlSession =sqlSessionFactory.openSession();        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);        java.util.List
     
       list =userMapper.findUserByName("zhao");        sqlSession.close();        System.out.println(list);    }}
     

通过调用单独的文件连接数据库

• SqlMapConfig.xml

• db.properties（和SqlMapConfig.xml在同一目录下）

jdbc.driver=com.mysql.jdbc.Driverjdbc.url=jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8jdbc.username=rootjdbc.password=

pojo包装类型实现

• UserMapper.xml（定义用户信息综合查询，查询条件复杂）

         select id,username,sex,address from users where sex= #{employeeCustom.sex} and username like '%${employeeCustom.username}%';     

• UserQueryVo.java（包装对象）

package cn.itcast.mybatis.po;public class UserQueryVo {    private EmployeeCustom employeeCustom;    public EmployeeCustom getEmployeeCustom() {        return employeeCustom;    }    public void setEmployeeCustom(EmployeeCustom employeeCustom) {        this.employeeCustom = employeeCustom;    }}

• EmployeeCustom.java

package cn.itcast.mybatis.po;public class EmployeeCustom extends Employee{   }

• 测试文件

@Test    public void test1() throws Exception {        SqlSession sqlSession =sqlSessionFactory.openSession();        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);                //创建包装对象，设置查询条件        UserQueryVo userQueryVo= new UserQueryVo();        EmployeeCustom employeeCustom=new EmployeeCustom();        employeeCustom.setSex("nv");        employeeCustom.setUsername("zhou");        userQueryVo.setEmployeeCustom(employeeCustom);               //调用userMapper的方法        java.util.List
     
       list =userMapper.findUserList(userQueryVo);        sqlSession.close();         System.out.println(list);    }
     

动态sql判断

• UserMapper.xml(判断传入的sex和username是否为空，若是空则不进行拼接)

         select id,username,sex,address from users                                                               and sex= #{employeeCustom.sex}                                                         and username like '%${employeeCustom.username}%';                                                          

• 测试文件

@Test    public void test1() throws Exception {        SqlSession sqlSession =sqlSessionFactory.openSession();        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);        UserQueryVo userQueryVo= new UserQueryVo();        EmployeeCustom employeeCustom=new EmployeeCustom();        //employeeCustom.setSex("nv");//注释此句后，查询语句中没有sex这个条件        employeeCustom.setUsername("zhou");        userQueryVo.setEmployeeCustom(employeeCustom);        java.util.List
     
       list =userMapper.findUserList(userQueryVo);        sqlSession.close();         System.out.println(list);    }
     

** 进行select * from users where id=1 or id=10 or id=11 ;**

• 在上面的UserMapper.xml中添加

                      
                       
      
                             id=#{user_id}                 
      
     

• 测试文件

@Test    public void test1() throws Exception {        SqlSession sqlSession =sqlSessionFactory.openSession();        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);        UserQueryVo userQueryVo= new UserQueryVo();        EmployeeCustom employeeCustom=new EmployeeCustom();        //employeeCustom.setSex("nv");        employeeCustom.setUsername("zhou");        java.util.List
     
       ids =new ArrayList
      
       ();        ids.add(1);        ids.add(10);        ids.add(14);        userQueryVo.setIds(ids);        userQueryVo.setEmployeeCustom(employeeCustom);        java.util.List
       
         list =userMapper.findUserList(userQueryVo);        sqlSession.close();         System.out.println(list);    }