mybatis详解-(8)配置自增主键

延续上一篇增删改查，在添加的时候使用的是数据库的自增主键，如果换成oracle这种没有自增主键的就无法实现，并且保存完成之后，在程序中是获取不到对象id的。我们打印保存后的对象如下：

1.未配置主键自增

    @Test    public void testMybatisAdd() {//测试添加            SqlSessionFactory sqlSessionFactory = null;            SqlSession sqlSession = null;            try {                sqlSessionFactory = getSqlSessionFactory();                //openSession可以添加参数，无参数表示不会自动提交，需要手动提交                sqlSession = sqlSessionFactory.openSession();//              sqlSession = sqlSessionFactory.openSession(true);                EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);                Employee employee = new Employee();                //数据库设置id自增                employee.setLastName("huanan");                employee.setEmail("[e-mail]");                employee.setGender("2");                mapper.addEmployee(employee);                System.out.println(employee);                sqlSession.commit();            } catch (IOException e) {                e.printStackTrace();            } finally {                sqlSession.close();            }    }

DEBUG - ooo Using Connection [com.mysql.jdbc.JDBC4Connection@184f6be2]
DEBUG - ==> Preparing: insert into mybatis_employee (last_name,email,gender) values (?,?,?);
DEBUG - ==> Parameters: huanan(String), [e-mail](String), 2(String)
Employee [id=null, lastName=huanan, email=[e-mail], gender=2]

这里打印的id=null，mybatis可以通过配置，自动生成主键

2.配置主键自增

在insert 标签中添加两个值
useGeneratedKeys=”true”表示使用自增主键
keyProperty=”id”表示id为自增主键

<!-- 插入方法 -->    <insert id="addEmployee" parameterType="org.mybatis.crud.Employee" useGeneratedKeys="true" keyProperty="id">        insert into mybatis_employee         (last_name,email,gender)         values         (#{lastName},#{email},#{gender});    </insert>

再次测试添加方法，可以获取到主键的值id=7

DEBUG - ooo Using Connection [com.mysql.jdbc.JDBC4Connection@1f7030a6]
DEBUG - ==> Preparing: insert into mybatis_employee (last_name,email,gender) values (?,?,?);
DEBUG - ==> Parameters: hussanan(String), [e-mail](String), 2(String)
Employee [id=7, lastName=hussanan, email=[e-mail], gender=2]

3.不存在自增主键数据库如何配置

<!-- 插入方法oracle -->    <insert id="addEmployeeo">        <!--         keyProperty=id需要赋值主键的属性，一般都是id         order=before表示在插入之前执行该查询        resultType=Integer表示返回值为integer类型        -->        <selectKey keyProperty="id" order="BEFORE" resultType="Integer">            select employees_seq.nextval from dual;        </selectKey>        insert into mybatis_employee         (id,last_name,email,gender)         values         (#{id},#{lastName},#{email},#{gender});    </insert>