mybatis开发Dao

参考文献:https://blog.csdn.net/u013036274/article/details/55668317

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

<mapper namespace="cn.itcast.mybatis.mapper.UserMapper"> <select id="findUserById" parameterType="int" resultType="cn.itcast.mybatis.po.Employee"> select id,username,sex,address from users where id=#{id}; </select> 

• 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<Employee> 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

<mapper resource="mapper/UserMapper.xml"/> 

• 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<Employee> 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

<properties resource="db.properties"></properties> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="${jdbc.driver}"/> <property name="url" value="${jdbc.url}"/> <property name="username" value="${jdbc.username}"/> <property name="password" value="${jdbc.password}"/> </dataSource> </environment> </environments> 

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

jdbc.driver=com.mysql.jdbc.Driver jdbc.url=jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8 jdbc.username=root jdbc.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="findUserList" parameterType="cn.itcast.mybatis.po.UserQueryVo" resultType="cn.itcast.mybatis.po.EmployeeCustom"> select id,username,sex,address from users where sex= #{employeeCustom.sex} and username like '%${employeeCustom.username}%'; </select> 

• 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<EmployeeCustom> 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="findUserList" parameterType="cn.itcast.mybatis.po.UserQueryVo" resultType="cn.itcast.mybatis.po.EmployeeCustom"> select id,username,sex,address from users <where> <if test="employeeCustom!=null"> <if test="employeeCustom.sex!=null and employeeCustom.sex!=''"> and sex= #{employeeCustom.sex} </if> <if test="employeeCustom.username!=null and employeeCustom.username!=''"> and username like '%${employeeCustom.username}%'; </if> </if> </where> </select> 

• 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<EmployeeCustom> 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

<if test="ids!=null"> <!-- collection:指定输入对象中集合属性 item:每个遍历生成对象中 open:开始遍历时拼接串 close:结束遍历时拼接的串 separator:遍历两个对象须拼接的串 实现拼接 AND (id=1 or id=10 or id=13) --> <foreach collection="ids" item="user_id" open="AND (" close=")" separator="or"> id=#{user_id} </foreach> 

• 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<Integer> ids =new ArrayList<Integer>(); ids.add(1); ids.add(10); ids.add(14); userQueryVo.setIds(ids); userQueryVo.setEmployeeCustom(employeeCustom); java.util.List<EmployeeCustom> list =userMapper.findUserList(userQueryVo); sqlSession.close(); System.out.println(list); }