Custom Row Processor

In case column names in a database table and equivalent javabean object names are not similar then we can map them by using customized BasicRowProcessor object. See the example below.

To understand the above-mentioned concepts related to DBUtils, let us write an example which will run a read query. To write our example, let us create a sample application.

Following is the content of the Employee.java.

public class Employee {
   private int id;
   private int age;
   private String first;
   private String last;
   private String name;
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public int getAge() {
      return age;
   }
   public void setAge(int age) {
      this.age = age;
   }
   public String getFirst() {
      return first;
   }
   public void setFirst(String first) {
      this.first = first;
   }
   public String getLast() {
      return last;
   }
   public void setLast(String last) {
      this.last = last;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
}

Following is the content of the EmployeeHandler.java file.

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.BeanProcessor;
import org.apache.commons.dbutils.BasicRowProcessor;

public class EmployeeHandler extends BeanHandler<Employee> {

   public EmployeeHandler() {
      super(Employee.class, new BasicRowProcessor(new BeanProcessor(mapColumnsToFields())));
   }

   @Override
   public Employee handle(ResultSet rs) throws SQLException {
      Employee employee = super.handle(rs);
      employee.setName(employee.getFirst() +", " + employee.getLast());
      return employee;
   }
   
   public static Map<String, String> mapColumnsToFields() {
      Map<String, String> columnsToFieldsMap = new HashMap<>();
      columnsToFieldsMap.put("ID", "id");
      columnsToFieldsMap.put("AGE", "age");        
      return columnsToFieldsMap;
   }
}

Following is the content of the MainApp.java file.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;

public class MainApp {
   // JDBC driver name and database URL
   static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";  
   static final String DB_URL = "jdbc:mysql://localhost:3306/emp";

   //  Database credentials
   static final String USER = "root";
   static final String PASS = "admin";

   public static void main(String[] args) throws SQLException {
      Connection conn = null;
      QueryRunner queryRunner = new QueryRunner();      
      DbUtils.loadDriver(JDBC_DRIVER);                 
      conn = DriverManager.getConnection(DB_URL, USER, PASS);        
      EmployeeHandler employeeHandler = new EmployeeHandler();

      try {
         Employee emp = queryRunner.query(conn,
           "SELECT * FROM employees WHERE first=?", employeeHandler, "Sumit");
         
         //Display values
         System.out.print("ID: " + emp.getId());
         System.out.print(", Age: " + emp.getAge());
         System.out.print(", Name: " + emp.getName());
      } finally {
         DbUtils.close(conn);
      }              
   }
}

Once you are done creating the source files, let us run the application. If everything is fine with your application, it will print the following message.

ID: 103, Age: 28, Name: Sumit, Mittal