Thursday, 29 April 2021

Spring jpa: @Param Named parameters: bind method parameter to the query

@Param annotation is used to give a method parameter a concrete name and bind the name in the query.

 

Example

@Query("SELECT e FROM Employee e WHERE e.firstName = :fName OR e.lastName = :lName")
public List<Employee> getEmployeesByFirstNameOrLastName(@Param("fName") String firstName, @Param("lName") String lastName);

 

Value of ‘firstName’ is replaced at :fName and value of lastName is replaced at :lName.

 

Find the below working application.

 

Step 1: Create new maven project ‘named-parameter-demo’.

 

Step 2: Update pom.xml with maven dependencies.

 

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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.sample.app</groupId>
  <artifactId>named-parameter-demo</artifactId>
  <version>1</version>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.4.0</version>
  </parent>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>


  <dependencies>

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>


    <dependency>
      <groupId>com.h2database</groupId>
      <artifactId>h2</artifactId>
    </dependency>


  </dependencies>
</project>

 

Step 3: Create application.properties file in src/main/resources folder.

 

application.properties

logging.level.root=WARN
logging.level.org.hibernate=ERROR

## 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

## JPA specific properties
# Creates the schema, destroying previous data.
spring.jpa.hibernate.ddl-auto=create

spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

spring.jpa.show-sql=false
spring.jpa.properties.hibernate.format_sql=false

## 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

spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true

 

Step 4: Define Employee entity class.

 

Employee.java

package com.sample.app.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "my_employee")
public class Employee {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private int id;

  @Column(name = "first_name")
  private String firstName;

  @Column(name = "last_name")
  private String lastName;

  @Column(name = "age")
  private int age;

  @Column(name = "salary")
  private double salary;

  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;
  }

  public int getAge() {
    return age;
  }

  public void setAge(int age) {
    this.age = age;
  }

  public double getSalary() {
    return salary;
  }

  public void setSalary(double salary) {
    this.salary = salary;
  }

  public static EmployeeBuilder builder() {
    return new EmployeeBuilder();
  }

  public static class EmployeeBuilder {
    private Employee emp;

    public EmployeeBuilder() {
      emp = new Employee();
    }

    public EmployeeBuilder firstName(String firstName) {
      emp.setFirstName(firstName);
      return this;
    }

    public EmployeeBuilder lastName(String lastName) {
      emp.setLastName(lastName);
      return this;
    }

    public EmployeeBuilder age(int age) {
      emp.setAge(age);
      return this;
    }

    public EmployeeBuilder salary(double salary) {
      emp.setSalary(salary);
      return this;
    }

    public Employee build() {
      return emp;
    }
  }

  @Override
  public String toString() {
    StringBuilder builder = new StringBuilder();
    builder.append("Employee [id=").append(id).append(", firstName=").append(firstName).append(", lastName=")
        .append(lastName).append(", age=").append(age).append(", salary=").append(salary).append("]");
    return builder.toString();
  }

}

 

Step 5: Define EmployeeRepository interface.

 

EmployeeRepository.java

package com.sample.app.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;

import com.sample.app.entity.Employee;

public interface EmployeeRepository extends JpaRepository<Employee, Integer> {

  @Query("SELECT e FROM Employee e WHERE e.firstName = :fName OR e.lastName = :lName")
  public List<Employee> getEmployeesByFirstNameOrLastName(@Param("fName") String firstName,
      @Param("lName") String lastName);
}

 

Step 6: Define main application class.

 

App.java

package com.sample.app;

import java.util.List;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

import com.sample.app.entity.Employee;
import com.sample.app.repository.EmployeeRepository;

@SpringBootApplication
public class App {

  public static void main(String args[]) {
    SpringApplication.run(App.class, args);
  }

  public void printEmployees(Iterable<Employee> emps, String msg) {
    System.out.println(msg);
    for (Employee emp : emps) {
      System.out.println(emp);
    }

    System.out.println();
  }

  @Bean
  public CommandLineRunner demo(EmployeeRepository employeeRepository) {
    return (args) -> {
      Employee emp1 = Employee.builder().firstName("Ram").lastName("Gurram").age(32).salary(100000.23).build();
      Employee emp2 = Employee.builder().firstName("Ram").lastName("Chelli").age(43).salary(60000).build();
      Employee emp3 = Employee.builder().firstName("Gopi").lastName("Battu").age(45).salary(1000000).build();
      Employee emp4 = Employee.builder().firstName("Ram").lastName("Srikanth").age(39).salary(60000).build();
      Employee emp5 = Employee.builder().firstName("Surendra").lastName("Sami").age(32).salary(100000.23).build();

      employeeRepository.save(emp1);
      employeeRepository.save(emp2);
      employeeRepository.save(emp3);
      employeeRepository.save(emp4);
      employeeRepository.save(emp5);

      List<Employee> emps = employeeRepository.getEmployeesByFirstNameOrLastName("Ram", "Sami");
      printEmployees(emps, "All the employees whose firstName is 'Ram' or lastName is 'Sami'");

    };
  }

}

 

Total project structure looks like below.

 


 

You can download complete working application from below link.

https://github.com/harikrishna553/springboot/tree/master/jpa/named-parameter-demo

 

 

 

 

 

 

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