iBATIS - Result Maps

The resultMap element is the most important and powerful element in iBATIS. You can reduce up to 90% JDBC coding using iBATIS ResultMap and in some cases, it allows you to do things that JDBC does not even support.

The design of ResultMaps is such that simple statements don't require explicit result mappings at all, and more complex statements require no more than is absolutely necessary to describe the relationships.

This chapter provides just a simple introduction of iBATIS ResultMaps.

We have the following EMPLOYEE table in MySQL −

CREATE TABLE EMPLOYEE (
   id INT NOT NULL auto_increment,
   first_name VARCHAR(20) default NULL,
   last_name  VARCHAR(20) default NULL,
   salary     INT  default NULL,
   PRIMARY KEY (id)
);

This table has two records as follows −

mysql> select * from EMPLOYEE;
+----+------------+-----------+--------+
| id | first_name | last_name | salary |
+----+------------+-----------+--------+
|  1 | Zara       | Ali       |   5000 |
|  2 | Roma       | Ali       |   3000 |
+----+------------+-----------+--------+
2 row in set (0.00 sec)

Employee POJO Class

To use iBATIS ResultMap, you do not need to modify the Employee.java file. Let us keep it as it was in the last chapter.

public class Employee {
   private int id;
   private String first_name; 
   private String last_name;   
   private int salary;  

   /* Define constructors for the Employee class. */
   public Employee() {}
  
   public Employee(String fname, String lname, int salary) {
      this.first_name = fname;
      this.last_name = lname;
      this.salary = salary;
   }

   /* Here are the required method definitions */
   public int getId() {
      return id;
   }
 
   public void setId(int id) {
      this.id = id;
   }
 
   public String getFirstName() {
      return first_name;
   }
 
   public void setFirstName(String fname) {
      this.first_name = fname;
   }
 
   public String getLastName() {
      return last_name;
   }
 
   public void setlastName(String lname) {
      this.last_name = lname;
   }
 
   public int getSalary() {
      return salary;
   }
 
   public void setSalary(int salary) {
      this.salary = salary;
   }

} /* End of Employee */

Employee.xml File

Here we would modify Employee.xml to introduce <resultMap></resultMap> tag. This tag would have an id which is required to run this resultMap in our <select> tag's resultMap attribute.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sqlMap PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN" "http://ibatis.apache.org/dtd/sql-map-2.dtd">

<sqlMap namespace="Employee">

   <!-- Perform Insert Operation -->
 
   <insert id="insert" parameterClass="Employee">
      INSERT INTO EMPLOYEE(first_name, last_name, salary)
      values (#first_name#, #last_name#, #salary#)

      <selectKey resultClass="int" keyProperty="id">
         select last_insert_id() as id
      </selectKey>
   </insert>

   <!-- Perform Read Operation -->
   <select id="getAll" resultClass="Employee">
      SELECT * FROM EMPLOYEE
   </select>

   <!-- Perform Update Operation -->
   <update id="update" parameterClass="Employee">
      UPDATE EMPLOYEE
      SET    first_name = #first_name#
      WHERE  id = #id#
    </update>

   <!-- Perform Delete Operation -->
   <delete id="delete" parameterClass="int">
      DELETE FROM EMPLOYEE
      WHERE  id = #id#
   </delete>

   <!-- Using ResultMap -->
   <resultMap id="result" class="Employee">
      <result property="id" column="id"/>
      <result property="first_name" column="first_name"/>
      <result property="last_name" column="last_name"/>
      <result property="salary" column="salary"/>
   </resultMap> 
 
   <select id="useResultMap" resultMap="result">
      SELECT * FROM EMPLOYEE
      WHERE id=#id#
   </select>

</sqlMap>

IbatisResultMap.java File

This file has application level logic to read records from the Employee table using ResultMap −

import com.ibatis.common.resources.Resources;
import com.ibatis.sqlmap.client.SqlMapClient;
import com.ibatis.sqlmap.client.SqlMapClientBuilder;

import java.io.*;
import java.sql.SQLException;
import java.util.*;

public class IbatisResultMap{
   public static void main(String[] args)
   throws IOException,SQLException{
      Reader rd = Resources.getResourceAsReader("SqlMapConfig.xml");
      SqlMapClient smc = SqlMapClientBuilder.buildSqlMapClient(rd);

      int id = 1;
      System.out.println("Going to read record.....");
      Employee e = (Employee)smc.queryForObject ("Employee.useResultMap", id);

      System.out.println("ID:  " + e.getId());
      System.out.println("First Name:  " + e.getFirstName());
      System.out.println("Last Name:  " + e.getLastName());
      System.out.println("Salary:  " + e.getSalary());
      System.out.println("Record read Successfully ");
   }
} 

Compilation and Run

Here are the steps to compile and run the above-mentioned software. Make sure you have set PATH and CLASSPATH appropriately before proceeding for compilation and execution.

• Create Employee.xml as shown above.
• Create Employee.java as shown above and compile it.
• Create IbatisResultMap.java as shown above and compile it.
• Execute IbatisResultMap binary to run the program.

You would get the following result which is a read operation on the EMPLOYEE table.

Going to read record.....
ID:  1
First Name:  Zara
Last Name:  Ali
Salary:  5000
Record read Successfully