MyBatis custom TypeHandler not executed when put in <result> tag

Question

I have a <resultMap> with custom typeHandler for one of the result properties:

<resultMap id="foo" type="hashmap">
    ... 
    <result property="SERVICES_XML" javaType="string" jdbcType="CLOB" typeHandler="com.foo.bar.OracleClobTypeHandler" />
    ...
</resultMap>

No matter which property I attach my handler to (I mean this is not CLOB-specific issue, tried with VARCHAR, too), the handler won't get called when I fetch results from database.

I have set breakpoints in all methods of my custom handler:

public class OracleClobTypeHandler implements TypeHandler<String> {

  @Override
  public void setParameter(PreparedStatement ps, int i, String parameter, JdbcType jdbcType) throws SQLException {
    log.debug("setParameter called");   <================ BREAKPOINT HERE
  }

  @Override
  public String getResult(ResultSet rs, String columnName)
        throws SQLException {
    log.debug("getResult 2 called");    <================ BREAKPOINT HERE
    return "";
  }

  @Override
  public String getResult(ResultSet rs, int columnIndex)
        throws SQLException {
    log.debug("getResult 2 called");    <================ BREAKPOINT HERE
    return "";
  }

  @Override
  public String getResult(CallableStatement cs, int columnIndex)
        throws SQLException {
    log.debug("getResult 3 called");    <================ BREAKPOINT HERE
    return "";
  }
}

Clearly none of the above methods is executed.

I've tried to put <typeHandler javaType="java.lang.String" jdbcType="CLOB" handler="com.foo.bar.OracleClobTypeHandler"/> in myBatis <configuration>, but this didn't work too.
Neither did anything else, including extending TypeHandler<Object> and so on.

What am I doing wrong?

Answer 1

After digging a long, long while I have finally found the answer.

This seems to be a bug in myBatis.

In order to get your handlers to work for <result> elements, you have to specify column attribute explicitly even if property attribute already matches column name and field name in bean.
In my case, it looks like this:

 <result property="SERVICES_XML" column="SERVICES_XML" javaType="string" jdbcType="CLOB" typeHandler="com.foo.bar.OracleClobTypeHandler" />

Note that the above change will also cause handlers defined in <configuration> tag to work, so inline typeHandler may be no longer necessary - that was my case. I ended up with:

<configuration>
  <typeHandlers>
    <typeHandler javaType="java.lang.String" jdbcType="CLOB" handler="com.foo.bar.OracleClobTypeHandler"/>        
  </typeHandlers>
</configuration>

and

<result property="SERVICES_XML" column="SERVICES_XML" javaType="string" jdbcType="CLOB" />

Answer 2

Although this question is 3 years old now, I'd rather bet the issue is related to the fact that Oracle 'uppercases' columns name retrieved from result metadata, while case sensitive java object properties name usually respect camel case.

Then explicit column-property mapping is required unless you use quoted aliases in the SQL query. The question has been asked here. And unlike what is said in the latest comment, I have observed that ORDER BY quoted alias works.