get auto-genearated key for the inserted record in mybatis

Question

I am working under a web application which use spring mvc + mybatis + mysql.

And I found that I can not get the auto-generated key for the last inserted record (I have googled so much).

This is the related configuration(take the model 'Post' for example):

spring.xml:

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
    //omitted
</bean>

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="configLocation" value="config.xml" />
</bean>

<bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
    <constructor-arg index="0" ref="sqlSessionFactory" />
</bean>

mybatis config.xml

<configuration>
    <typeAliases>
        <typeAlias alias="Post" type="com.king.model.Post" />
    </typeAliases>
    <mappers>
        <mapper resource="com/king/model/PostMapper.xml" />
    </mappers>
</configuration>

PostMapper.xml:

<mapper namespace="com.king.model.PostMapper">
    <insert id="insert" parameterType="Post">
        insert into posts (title,body,created_at,updated_at) values (#{title},#{body},#{createDate},#{updateDate})
    </insert>
</mapper>

Dao:

public abstract class AbstractSimpleDaoImpl<T> extends SqlSessionDaoSupport{
    @Override
    public int add(T entity) {
        return getSqlSession().insert(getMapperNamespace() + ".insert", entity);
    }

    protected abstract String getMapperNamespace();
}

public class PostDao extends AbstractSimpleDaoImpl<Post> {
    @Override
    protected String getMapperNamespace() {
        return "com.king.model.PostMapper";
    }
}

---

However,when I insert a new Post to database:

postDao.add(post);

I can not get the generated id for the inserted post. I always get 1. I know this is the row-affected number.

Also,I read the mybatis guide,and I tried this:

<insert id="insert" parameterType="Post" useGeneratedKeys="true" keyProperty="id">

But it seems that,this does not work.

How to fix it?

Answer 1

In fact the following works:

<insert id="insert" parameterType="Post" useGeneratedKeys="true" keyProperty="id">

postDao.add(post);

will return 1 as before,but post.getId() will get the key.

Answer 2

This can be done using annotations as well.

final String INSERT = "insert into posts (title,body,created_at,updated_at) values (#{title},#{body},#{createDate},#{updateDate})";

@Insert(INSERT)
@Options(useGeneratedKeys = true, keyProperty = "id", keyColumn = "id")
void insert(Post post) throws Exception;

Set keyProperty as the Java variable name.

Set keyColumn as the column name in the database.

After insert, post.getId() will have your generated ID.