- Apache Commons DBUtils Tutorial
- DBUtils - Home
- DBUtils - Overview
- DBUtils - Environment Setup
- DBUtils - First Application
- Basic CRUD Examples
- DBUtils - Create Query
- DBUtils - Read Query
- DBUtils - Update Query
- DBUtils - Delete Query
- Apache Commons DBUtils Examples
- DBUtils - QueryRunner interface
- DBUtils - AsyncQueryRunner interface
- DBUtils - ResultSetHandler interface
- DBUtils - BeanHandler Class
- DBUtils - BeanListHandler Class
- DBUtils - ArrayListHandler Class
- DBUtils - MapListHandler Class
- Advanced DBUtils Examples
- DBUtils - Custom Handler
- DBUtils - Custom Row Processor
- DBUtils - Using DataSource
- DBUtils Useful Resources
- DBUtils - Quick Guide
- DBUtils - Useful Resources
- DBUtils - Discussion
ResultSetHandler interface
The org.apache.commons.dbutils.ResultSetHandler interface is responsible to convert ResultSets into objects.
Class Declaration
Following is the declaration for org.apache.commons.dbutils.ResultSetHandler class −
public interface ResultSetHandler<T>
Usage
Step 1 − Create a connection object.
Step 2 − Create implementation of ResultSetHandler.
Step 3 − Pass resultSetHandler to QueryRunner object, and make database operations.
Example
Following example will demonstrate how to map a record using ResultSetHandler class. We'll read one of the available record in Employee Table.
Syntax
Employee emp = queryRunner.query(conn, "SELECT * FROM employees WHERE first=?", resultHandler, "Sumit");
Where,
resultHandler − ResultSetHandler 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 java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.util.Arrays; import org.apache.commons.dbutils.DbUtils; import org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.ResultSetHandler; 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<Object[]> handler = new ResultSetHandler<Object[]>() { public Object[] handle(ResultSet rs) throws SQLException { if (!rs.next()) { return null; } ResultSetMetaData meta = rs.getMetaData(); int cols = meta.getColumnCount(); Object[] result = new Object[cols]; for (int i = 0; i < cols; i++) { result[i] = rs.getObject(i + 1); } return result; } }; try { Object[] result = queryRunner.query(conn, "SELECT * FROM employees WHERE id=?", handler, 103); //Display values System.out.print("Result: " + Arrays.toString(result)); } 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.
Connecting to database... Result: [103, 33, Sumit, Mittal]