Mapping list of strings in mybatis

Question

I want to retieve list of strings using mybatis.I am using following code ,but getting illegalArgument exception as follow :

   javax.servlet.ServletException: org.mybatis.spring.MyBatisSystemException: SqlSession operation; nested exception is java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for java.lang.Object.toString
        org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:515)
        org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419)

Mybatis configuration :

<select id="fetchIds" resultType="java.lang.String" >
        SELECT distinct ids 
        FROM abc.emp 
</select>

My Dao method is :

@Override
    public List<String> fetchIds() {
        System.out.println("Inside fetchIds");
        SqlSession session = null;
        List retrieveList = null;
        try{
         session = sqlSessionFactory.openSession();
         System.out.println("After session creation:"+session);
         retrieveList =  session.selectList("fetchIds");
        }finally{
            session.close();
        }

        return retrieveList;

    }

Can anybody please suggest how we can achieve this.

Answer 1

Define the List to List<String>. Here your code would look like

<select id="fetchIds" resultType="string" >
        SELECT distinct ids 
        FROM abc.emp 
</select>

And Dao Method

@Override
    public List<String> fetchIds() {
        System.out.println("Inside fetchIds");
        SqlSession session = null;
        List<String> retrieveList = null;
        try{
         session = sqlSessionFactory.openSession();
         System.out.println("After session creation:"+session);
         retrieveList =  session.selectList("fetchIds");
        }finally{
            session.close();
        }

        return retrieveList;

    }

The mapper interface.java file has method signature as follows.

String[] fetchIds()throws Exception;