第一种方法:

insert INTO student(name) VALUES("南亚");
SELECT @@identity

第二种方法:

insert INTO student(name) VALUES("南亚");
SELECT LAST_INSERT_ID()

在mapper.xml中写法:

<insert id="insertStudentCacheId" >
  insert into student(name,age,score) values(#{name},#{age},#{score})
    <!-- order属性:表示先插入还是先生成id;mysql是先插入后再生成id,oracle是先生成id再插入 -->

    <!-- SELECT @@identity 查询出的值初始化keyProperty属性  -->

    <selectKey resultType="int"  keyProperty="id" order="AFTER">
    SELECT @@identity
  </selectKey>
</insert>

测试代码:

@Test
public void test02(){
  Student student = new Student("南非", 20, 99.5);
  System.out.println("插入前:student="+student);
  dao.insertStudentCacheId(student);
  System.out.println("插入后:student="+student);

}