Commons DBUtils - BeanHandler Class

Advertisements

Previous Page
Next Page  

The org.apache.commons.dbutils.BeanHandler is the implementation of ResultSetHandler interface and is responsible to convert the first ResultSet row into a JavaBean. This class is thread safe.

Class Declaration

Following is the declaration for org.apache.commons.dbutils.BeanHandler class −

public class BeanHandler<T>
   extends Object implements ResultSetHandler<T>

Usage

  • Step 1 − Create a connection object.

  • Step 2 − Get implementation of ResultSetHandler as BeanHandler object.

  • Step 3 − Pass resultSetHandler to QueryRunner object, and make database operations.

Example

Following example will demonstrate how to read a record using BeanHandler class. We'll read one of the available record in Employees Table and map it to Employee bean.

Syntax

Employee emp = queryRunner.query(conn, "SELECT * FROM employees WHERE first=?", resultHandler, "Sumit");

Where,

  • resultHandler − BeanHandler object to map result set to Employee object.

  • queryRunner − QueryRunner object to read employee object from database.

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.

Step Description
1 Update the file MainApp.java created under chapter DBUtils - First Application.
2 Compile and run the application as explained below.

Following is the content of the Employee.java.

public class Employee {
   private int id;
   private int age;
   private String first;
   private String last;
   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;
   }
}

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;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;

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();
      
      //Step 1: Register JDBC driver
      DbUtils.loadDriver(JDBC_DRIVER);

      //Step 2: Open a connection
      System.out.println("Connecting to database...");
      conn = DriverManager.getConnection(DB_URL, USER, PASS);

      //Step 3: Create a ResultSet Handler to handle Employee Beans
      ResultSetHandler<Employee> resultHandler 
         = new BeanHandler<Employee>(Employee.class);

      try {
         Employee emp = queryRunner.query(conn, "SELECT * FROM employees WHERE first=?",
               resultHandler, "Sumit");
         //Display values
         System.out.print("ID: " + emp.getId());
         System.out.print(", Age: " + emp.getAge());
         System.out.print(", First: " + emp.getFirst());
         System.out.println(", Last: " + emp.getLast());
      } 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, First: Sumit, Last: Mittal
Advertisements