The org.springframework.jdbc.core.RowMapper<T> interface is used by JdbcTemplate for mapping rows of a ResultSet on a per-row basis. Implementations of this interface perform the actual work of mapping each row to a result object. SQLExceptions if any thrown will be caught and handled by the calling JdbcTemplate.
Interface Declaration
Following is the declaration for org.springframework.jdbc.core.RowMapper<T> interface −
public interface RowMapper<T>
Usage
Step 1 − Create a JdbcTemplate object using a configured datasource.
Step 2 − Create a StudentMapper object implementing RowMapper interface.
Step 3 − Use JdbcTemplate object methods to make database operations while using StudentMapper object.
Following example will demonstrate how to read a query using spring jdbc. We'll map read records from Student Table to Student object using StudentMapper object.
Syntax
List <Student> students = jdbcTemplateObject.query(SQL, new StudentMapper());
Where
jdbcTemplateObject − StudentJDBCTemplate object to read student records from database.
StudentMapper − StudentMapper object to map student records to student objects.
To understand the above-mentioned concepts related to Spring JDBC, let us write an example which will read a query and map result using StudentMapper object. To write our example, let us have a working Eclipse IDE in place and use the following steps to create a Spring application.
Step Description
1 Update the project Student created under chapter Spring JDBC - First Application.
2 Update the bean configuration and run the application as explained below.
Following is the content of the Student.java file.
public class Student {
private Integer age;
private String name;
private Integer id;
public void setAge(Integer age) {
this.age = age;
}
public Integer getAge() {
return age;
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setId(Integer id) {
this.id = id;
}
public Integer getId() {
return id;
}
}
Following is the content of the StudentMapper.java file.
import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.jdbc.core.RowMapper;
public class StudentMapper implements RowMapper<Student> {
public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
Student student = new Student();
student.setId(rs.getInt("id"));
student.setName(rs.getString("name"));
student.setAge(rs.getInt("age"));
return student;
}
}
Following is the content of the Data Access Object interface file StudentDao.java.
import java.util.List;
import javax.sql.DataSource;
public interface StudentDao {
/**
* This is the method to be used to initialize
* database resources ie. connection.
*/
public void setDataSource(DataSource ds);
/**
* This is the method to be used to list down
* all the records from the Student table.
*/
public List<Student> listStudents();
}
Following is the implementation class file StudentJDBCTemplate.java for the defined DAO interface StudentDAO.
import java.util.List;
import javax.sql.DataSource;
import org.springframework.jdbc.core.JdbcTemplate;
public class StudentJDBCTemplate implements StudentDao {
private DataSource dataSource;
private JdbcTemplate jdbcTemplateObject;
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
this.jdbcTemplateObject = new JdbcTemplate(dataSource);
}
public List<Student> listStudents() {
String SQL = "select * from Student";
List <Student> students = jdbcTemplateObject.query(SQL, new StudentMapper());
return students;
}
}
Following is the content of the MainApp.java file
import java.util.List
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.javahubpoint.StudentJDBCTemplate;
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
StudentJDBCTemplate studentJDBCTemplate = (StudentJDBCTemplate)context.getBean("studentJDBCTemplate");
System.out.println("------Listing Multiple Records--------" );
List<Student> students = studentJDBCTemplate.listStudents();
for (Student record : students) {
System.out.print("ID : " + record.getId() );
System.out.print(", Name : " + record.getName() );
System.out.println(", Age : " + record.getAge());
}
}
}
Following is the configuration file Beans.xml.
<beans xmlns = "http://www.springframework.org/schema/beans"
xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation = "http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd ">
<!-- Initialization for data source -->
<bean id = "dataSource"
class = "org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name = "driverClassName" value = "com.mysql.cj.jdbc.Driver"/>
<property name = "url" value = "jdbc:mysql://localhost:3306/TEST"/>
<property name = "username" value = "root"/>
<property name = "password" value = "admin"/>
</bean>
<!-- Definition for studentJDBCTemplate bean -->
<bean id = "studentJDBCTemplate"
class = "com.javahubpoint.StudentJDBCTemplate">
<property name = "dataSource" ref = "dataSource" />
</bean>
</beans>
Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message.
------Listing Multiple Records--------
ID : 1, Name : Zara, Age : 17
ID : 3, Name : Ayan, Age : 18