mybatis的增删该查

1.查找所有的用户

mybatis-config.xml配置文件用于连接数据库，打开和关闭session

<?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="yy">
      <environment id="yy">
         <transactionManager type="JDBC"></transactionManager>
         <dataSource type="POOLED">
          <property name="driver" value="oracle.jdbc.driver.OracleDriver"/>
       
          <property name="url" value="jdbc:oracle:thin:@172.16.17.158:1521:orcl"/>
          <property name="username" value="scott"/>
          <property name="password" value="tiger"/>
         </dataSource>
      </environment>
  </environments>
  <mappers>
  <mapper   resource="com/yh/mb/dao/EmpDao-mapper.xml"/>
  </mappers>
</configuration>

EmpDao-mapper.xml实体类的映射文件，编写sql语句

<select id="empCout"  resultType="int">
select count(1) from emp
</select>

resultType是指sql语句的返回值类型，可以起别名
EmpDao.java，实现类

public int empCount() {
        SqlSessionFactory sqlsf=null;
        SqlSession sqlsession=null;
        Reader reader=null;//配置文件字符输入流
        int count=0;
        try {
            reader=Resources.getResourceAsReader("mybatis-config.xml");
            sqlsf=new SqlSessionFactoryBuilder().build(reader);
            sqlsession=sqlsf.openSession();
            count=sqlsession.selectOne("com.yh.mb.dao.EmpDao.empCout");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            if(sqlsession!=null){
                sqlsession.close();
            }
                
        }                    
        return count;
    }

2.通过id进行查找

映射文件

<select id="getEmpById" resultType="Emp" parameterType="int">
select ename as empName from emp where empno=#{empNo}
</select>

resultType起了别名在配置文件中起别名

<typeAliases >
<typeAlias type="com.yh.mb.entity.Emp"  alias="Emp"/>
</typeAliases>

dao层的方法

public Emp getEmpById(Integer no) {
        SqlSession sqlsession=null;
        Emp emp=null;
        try {
            sqlsession=MyBatisUtil.getSession();
            emp=sqlsession.selectOne("com.yh.mb.dao.EmpDao.getEmpById", no);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            MyBatisUtil.closeSession();
        }
        
        return emp;
    }

Mytest.java测试单元

IEmpDao empDao=new EmpDao();
      @Test
      public void getEmpById(){
          Emp e=empDao.getEmpById(7944);
          System.out.println(e.getEmpName());
      }

2.多条件查询

用hashmap来放多个查询条件

<select id="getEmpByIdAndJob" resultType="Emp" parameterType="hashmap">
select ename as empName from emp where empno=#{empNo}and job=#{j}
</select>

dao层的方法

public Emp getEmpByIdAndJob(Integer no,String job){
       SqlSession sqlsession = null;
        Emp emp=null;
        try {
            sqlsession = MyBatisUtil.getSession();
            HashMap map=new HashMap();
            map.put("empNo",no);
            map.put("j",job);
            emp=sqlsession.selectOne("com.yh.mb.dao.EmpDao.getEmpByIdAndJob", map);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            MyBatisUtil.closeSession();
        }
        return emp;
   }

测试单元

 @Test
      public void getEmpByIdAndJob(){
          Emp e=empDao.getEmpByIdAndJob(9000, "CLERK");
          
          System.out.println(e.getEmpName());
      }