'queryForObject'
method can be used to retrieve the object by id.
Example
jdbcTemplate.queryForObject("SELECT
* FROM employees WHERE id=?", EMPLOYEE_ROW_MAPPER, id);
Step 1: Create Employee Row mapper.
private
static final RowMapper<Employee> EMPLOYEE_ROW_MAPPER = (rs, rowNum) ->
{
Employee emp1 = new Employee();
emp1.setId(rs.getInt("id"));
emp1.setFirstName(rs.getString("first_name"));
emp1.setLastName(rs.getString("last_name"));
return emp1;
};
Step 2: Use 'queryForObject' method to
retrieve the object for given id.
Employee
emp = jdbcTemplate.queryForObject("SELECT * FROM employees WHERE
id=?", EMPLOYEE_ROW_MAPPER, id);
Find the
below working application.
App.java
package com.sample.app;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.jdbc.core.JdbcTemplate;
import com.sample.app.entity.Employee;
import com.sample.app.repository.EmployeeRepository;
@SpringBootApplication
public class App {
private static final Logger log = LoggerFactory.getLogger(App.class);
@Autowired
JdbcTemplate jdbcTemplate;
@Autowired
EmployeeRepository employeeRepository;
public static void main(String args[]) {
SpringApplication.run(App.class, args);
}
@Bean
public CommandLineRunner demo() {
return (args) -> {
log.info("Creating tables");
jdbcTemplate.execute("DROP TABLE employees IF EXISTS");
jdbcTemplate.execute(
"CREATE TABLE employees (id serial, first_name VARCHAR(255), last_name VARCHAR(255), PRIMARY KEY(id)) ");
Employee emp1 = new Employee("Ram", "Gurram");
Employee emp2 = new Employee("Moutwika", "Maj");
Employee emp3 = new Employee("Anusha", "R");
employeeRepository.save(emp1);
employeeRepository.save(emp2);
employeeRepository.save(emp3);
System.out.println("\nPrinting All Employees\n");
List<Employee> emps = employeeRepository.all();
emps.forEach(customer -> System.out.println(customer));
Employee emp = employeeRepository.get(1);
System.out.println("Employee with id 1 : " + emp);
emp = employeeRepository.get(10);
System.out.println("Employee with id 10 : " + emp);
};
}
}
Employee.java
package com.sample.app.entity;
public class Employee {
private int id;
private String firstName;
private String lastName;
public Employee(int id, String firstName, String lastName) {
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
}
public Employee(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
public Employee() {}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("Employee [id=").append(id).append(", firstName=").append(firstName).append(", lastName=")
.append(lastName).append("]");
return builder.toString();
}
}
EmployeeRepository.java
package com.sample.app.repository;
import java.util.List;
import com.sample.app.entity.Employee;
public interface EmployeeRepository {
public Employee save(Employee emp);
public List<Employee> all();
public Employee get(int id);
}
EmployeeRepositoryImpl.java
package com.sample.app.repository.impl;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.dao.EmptyResultDataAccessException;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.PreparedStatementCreator;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.jdbc.support.GeneratedKeyHolder;
import org.springframework.jdbc.support.KeyHolder;
import org.springframework.stereotype.Repository;
import com.sample.app.entity.Employee;
import com.sample.app.repository.EmployeeRepository;
@Repository
public class EmployeeRepositoryImpl implements EmployeeRepository {
@Autowired
JdbcTemplate jdbcTemplate;
private static final RowMapper<Employee> EMPLOYEE_ROW_MAPPER = (rs, rowNum) -> {
Employee emp1 = new Employee();
emp1.setId(rs.getInt("id"));
emp1.setFirstName(rs.getString("first_name"));
emp1.setLastName(rs.getString("last_name"));
return emp1;
};
@Override
public Employee save(Employee emp) {
KeyHolder keyHolder = new GeneratedKeyHolder();
PreparedStatementCreator preparedStmtCreator = new PreparedStatementCreator() {
@Override
public PreparedStatement createPreparedStatement(Connection connection) throws SQLException {
PreparedStatement ps = connection.prepareStatement(
"INSERT INTO employees (first_name, last_name) VALUES (?, ?)", new String[] { "id" });
ps.setString(1, emp.getFirstName());
ps.setString(2, emp.getLastName());
return ps;
}
};
jdbcTemplate.update(preparedStmtCreator, keyHolder);
int id = (Integer) keyHolder.getKey();
Employee emp1 = new Employee();
jdbcTemplate.query("SELECT * FROM employees WHERE id = " + id, rs -> {
emp1.setId(rs.getInt("id"));
emp1.setFirstName(rs.getString("first_name"));
emp1.setLastName(rs.getString("last_name"));
});
return emp1;
}
@Override
public List<Employee> all() {
return jdbcTemplate.query("SELECT * FROM employees", EMPLOYEE_ROW_MAPPER);
}
@Override
public Employee get(int id) {
try {
return jdbcTemplate.queryForObject("SELECT * FROM employees WHERE id=?", EMPLOYEE_ROW_MAPPER, id);
} catch (EmptyResultDataAccessException e) {
return null;
}
}
}
application.properties
logging.level.root=WARN ## H2 specific properties spring.h2.console.enabled=true spring.h2.console.path=/h2 spring.datasource.url=jdbc:h2:file:~/db/myOrg.db;DB_CLOSE_ON_EXIT=FALSE;DB_CLOSE_DELAY=-1; spring.datasource.username=krishna spring.datasource.password=password123 spring.datasource.driverClassName=org.h2.Driver ## Database connection pooling properties # Number of ms to wait before throwing an exception if no connection is available. spring.datasource.max-wait=10000 # Maximum number of active connections that can be allocated from this pool at the same time. spring.datasource.tomcat.max-active=10 spring.datasource.tomcat.max-idle=5 spring.datasource.tomcat.min-idle=3
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>springJDBC</groupId>
<artifactId>springJDBC</artifactId>
<version>1</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.6.RELEASE</version>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
</dependency>
</dependencies>
</project>
Total
project structure looks like below.
Run App.java,
you can see below messages in console.
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.6.RELEASE)
Printing All Employees
Employee [id=1, firstName=Ram, lastName=Gurram]
Employee [id=2, firstName=Moutwika, lastName=Maj]
Employee [id=3, firstName=Anusha, lastName=R]
Employee with id 1 : Employee [id=1, firstName=Ram, lastName=Gurram]
Employee with id 10 : null
You can
download complete working application from this link.
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