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Spring Boot Rest Web Service
A Spring Boot Rest Web Service is a RESTful web service built using the Spring Boot framework. REST (Representational State Transfer) is a popular architectural style for building web services that allow clients to interact with server resources by sending HTTP requests and receiving HTTP responses.
A Spring Boot Rest Web Service typically exposes a set of REST endpoints that can be called by clients to perform specific actions. For example, a service might expose endpoints for creating, retrieving, updating, and deleting resources.
Spring Boot provides a number of tools and technologies that make it easier to build and deploy RESTful web services.
In the example below we are going to create REST web service that will be used to view/update Student information in the database table.
1. Go to Spring initializr website and create a Java Maven Project with dependencies: H2, Spring Data JPA and Web. Download the project zip and extract to a folder.
2. Import the project into IDE (I am using IntelliJ Idea). Pom.xml:
The <dependencies> section contains the project's dependencies. In this example, it includes several dependencies:
- spring-boot-starter-data-jpa: Spring Boot starter for working with relational databases and JPA.
- h2: An in-memory database for development and testing purposes.
- spring-boot-starter-test: Spring Boot starter for testing.
- spring-boot-starter-web: Spring Boot starter for building web applications.
The <build> section contains the build configuration for the project. In this case, it includes a single plugin:
spring-boot-maven-plugin: A Maven plugin that provides support for packaging and running Spring Boot applications.
<?xml version="1.0" encoding="UTF-8"?>
<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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.3</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
2. Create Student class in the com.example.demo.model package.
- The @Entity annotation is from the Java Persistence API (JPA) and marks this class as an entity, representing a table in a relational database.
- The @Table annotation specifies that the entity is mapped to a database table with the same name as the class (by default).
- The Student class has three fields: student_id: An int field annotated with @Id. This indicates that it is the primary key for the entity. name: A String field representing the name of the student. grade: A String field representing the grade of the student.
- The @GeneratedValue annotation with GenerationType.IDENTITY strategy is applied to the student_id field. This indicates that the value for this field will be automatically generated by the underlying database when a new entity is persisted.
- The class provides two constructors: The default constructor with no arguments. A parameterized constructor that takes name and grade as arguments to initialize the corresponding fields.
- Getter and setter methods are provided for all the fields to access and modify their values.
package com.example.demo.model;
import javax.persistence.*;
@Entity
@Table
public class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int student_id;
private String name;
private String grade;
public Student(){
}
public Student( String name, String grade) {
this.name = name;
this.grade = grade;
}
public int getStudent_id() {
return student_id;
}
public void setStudent_id(int student_id) {
this.student_id = student_id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getGrade() {
return grade;
}
public void setGrade(String grade) {
this.grade = grade;
}
}
3. Create StudentRepo class extending CrudRepository. CrudRepository will provide the Create, Read, Update and Delete methods.
package com.example.demo.dao;
import com.example.demo.model.Student;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
@Repository
public interface StudentRepo extends CrudRepository<Student, Long> {}
4. Create controller class StudentController.
- The @RestController annotation indicates that this class is a controller component that handles RESTful requests and automatically serializes/deserializes objects to/from JSON.
- The @Autowired annotation is used to inject an instance of the StudentRepo class, which is a repository interface for accessing and manipulating student data.
- The @GetMapping annotation is used to map HTTP GET requests to specific endpoints.
- The @PostMapping annotation is used to map HTTP POST requests.
- The @DeleteMapping annotation is used to map HTTP DELETE requests.
- The @PutMapping annotation is used to map HTTP PUT requests.
- The @PathVariable annotation is used to bind a path variable (e.g., {id}) from the request URL to a method parameter.
- The @RequestBody annotation is used to bind the request body (in JSON format) to a method parameter.
Here's a breakdown of the methods in the
StudentController class:getAllStudents() method:
Handles GET requests to the /students endpoint.
Calls the findAll() method of the StudentRepo instance to retrieve all students from the repository.
Returns a list of Student objects.
getStudents(Long id) method:
Handles GET requests to the /student/{id} endpoint.
Uses the findById(id) method of the StudentRepo instance to find a student by their ID.
Returns an Optional<Student> object, which either contains the found student or is empty.
addStudent(Student newStudent) method:
Handles POST requests to the /students endpoint.
Saves a new student object to the repository using the save(newStudent) method of the StudentRepo instance.
Returns the saved Student object.
removeStudent(Long id) method:
Handles DELETE requests to the /students/{id} endpoint.
Deletes a student from the repository by their ID using the deleteById(id) method of the StudentRepo instance.
updateStudent(Student newStudent, Long id) method:
Handles PUT requests to the /students/{id} endpoint. Finds a student by their ID using the findById(id) method of the StudentRepo instance.
If the student exists, updates their name and grade with the values from newStudent and saves the updated student using the save(student) method of the StudentRepo instance. If the student doesn't exist, creates a new student with the ID id from the path variable, sets its name and grade from newStudent, and saves it to the repository. Returns the updated or newly created Student object.
package com.example.demo.controller;
import com.example.demo.dao.StudentRepo;
import com.example.demo.model.Student;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;
import java.util.Optional;
@RestController
public class StudentController {
@Autowired
private StudentRepo repo;
@GetMapping("/students")
private List<Student> getAllStudents(){
return (List<Student>) repo.findAll();
}
@GetMapping("/student/{id}")
private Optional<Student> getStudents(@PathVariable Long id){
return repo.findById(id);
}
@PostMapping("/students")
private Student addStudent(@RequestBody Student newStudent){
return repo.save(newStudent);
}
@DeleteMapping("/students/{id}")
private void removeStudent(@PathVariable Long id){
repo.deleteById(id);
}
@PutMapping("/students/{id}")
private Student updateStudent(@RequestBody Student newStudent, @PathVariable Long id){
return repo.findById(id)
.map(student -> {
student.setName(newStudent.getName());
student.setGrade(newStudent.getGrade());
return repo.save(student);
})
.orElseGet(() -> {
newStudent.setStudent_id(Math.toIntExact(id));
return repo.save(newStudent);
});
}
}
5. Add below line in the application.properties file. This will make JPA queries appear in the log
spring.jpa.show-sql=true
6. Run the Spring Boot application and test using web service client (such as Postman)
DemoApplication.java
package com.example.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}"C:\Program Files\Java\jdk-11.0.15\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2021.2\lib\idea_rt.jar=65263:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2021.2\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\mail2\Downloads\demo\target\classes;D:\.m2\repository\org\springframework\boot\spring-boot-starter-data-jpa\2.7.3\spring-boot-starter-data-jpa-2.7.3.jar;D:\.m2\repository\org\springframework\boot\spring-boot-starter-aop\2.7.3\spring-boot-starter-aop-2.7.3.jar;D:\.m2\repository\org\springframework\spring-aop\5.3.22\spring-aop-5.3.22.jar;D:\.m2\repository\org\aspectj\aspectjweaver\1.9.7\aspectjweaver-1.9.7.jar;D:\.m2\repository\org\springframework\boot\spring-boot-starter-jdbc\2.7.3\spring-boot-starter-jdbc-2.7.3.jar;D:\.m2\repository\com\zaxxer\HikariCP\4.0.3\HikariCP-4.0.3.jar;D:\.m2\repository\org\springframework\spring-jdbc\5.3.22\spring-jdbc-5.3.22.jar;D:\.m2\repository\jakarta\transaction\jakarta.transaction-api\1.3.3\jakarta.transaction-api-1.3.3.jar;D:\.m2\repository\jakarta\persistence\jakarta.persistence-api\2.2.3\jakarta.persistence-api-2.2.3.jar;D:\.m2\repository\org\hibernate\hibernate-core\5.6.10.Final\hibernate-core-5.6.10.Final.jar;D:\.m2\repository\org\jboss\logging\jboss-logging\3.4.3.Final\jboss-logging-3.4.3.Final.jar;D:\.m2\repository\net\bytebuddy\byte-buddy\1.12.13\byte-buddy-1.12.13.jar;D:\.m2\repository\antlr\antlr\2.7.7\antlr-2.7.7.jar;D:\.m2\repository\org\jboss\jandex\2.4.2.Final\jandex-2.4.2.Final.jar;D:\.m2\repository\com\fasterxml\classmate\1.5.1\classmate-1.5.1.jar;D:\.m2\repository\org\hibernate\common\hibernate-commons-annotations\5.1.2.Final\hibernate-commons-annotations-5.1.2.Final.jar;D:\.m2\repository\org\glassfish\jaxb\jaxb-runtime\2.3.6\jaxb-runtime-2.3.6.jar;D:\.m2\repository\org\glassfish\jaxb\txw2\2.3.6\txw2-2.3.6.jar;D:\.m2\repository\com\sun\istack\istack-commons-runtime\3.0.12\istack-commons-runtime-3.0.12.jar;D:\.m2\repository\com\sun\activation\jakarta.activation\1.2.2\jakarta.activation-1.2.2.jar;D:\.m2\repository\org\springframework\data\spring-data-jpa\2.7.2\spring-data-jpa-2.7.2.jar;D:\.m2\repository\org\springframework\data\spring-data-commons\2.7.2\spring-data-commons-2.7.2.jar;D:\.m2\repository\org\springframework\spring-orm\5.3.22\spring-orm-5.3.22.jar;D:\.m2\repository\org\springframework\spring-context\5.3.22\spring-context-5.3.22.jar;D:\.m2\repository\org\springframework\spring-tx\5.3.22\spring-tx-5.3.22.jar;D:\.m2\repository\org\springframework\spring-beans\5.3.22\spring-beans-5.3.22.jar;D:\.m2\repository\org\slf4j\slf4j-api\1.7.36\slf4j-api-1.7.36.jar;D:\.m2\repository\org\springframework\spring-aspects\5.3.22\spring-aspects-5.3.22.jar;D:\.m2\repository\com\h2database\h2\2.1.214\h2-2.1.214.jar;D:\.m2\repository\org\springframework\boot\spring-boot-starter\2.7.3\spring-boot-starter-2.7.3.jar;D:\.m2\repository\org\springframework\boot\spring-boot\2.7.3\spring-boot-2.7.3.jar;D:\.m2\repository\org\springframework\boot\spring-boot-autoconfigure\2.7.3\spring-boot-autoconfigure-2.7.3.jar;D:\.m2\repository\org\springframework\boot\spring-boot-starter-logging\2.7.3\spring-boot-starter-logging-2.7.3.jar;D:\.m2\repository\ch\qos\logback\logback-classic\1.2.11\logback-classic-1.2.11.jar;D:\.m2\repository\ch\qos\logback\logback-core\1.2.11\logback-core-1.2.11.jar;D:\.m2\repository\org\apache\logging\log4j\log4j-to-slf4j\2.17.2\log4j-to-slf4j-2.17.2.jar;D:\.m2\repository\org\apache\logging\log4j\log4j-api\2.17.2\log4j-api-2.17.2.jar;D:\.m2\repository\org\slf4j\jul-to-slf4j\1.7.36\jul-to-slf4j-1.7.36.jar;D:\.m2\repository\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;D:\.m2\repository\org\yaml\snakeyaml\1.30\snakeyaml-1.30.jar;D:\.m2\repository\jakarta\xml\bind\jakarta.xml.bind-api\2.3.3\jakarta.xml.bind-api-2.3.3.jar;D:\.m2\repository\jakarta\activation\jakarta.activation-api\1.2.2\jakarta.activation-api-1.2.2.jar;D:\.m2\repository\org\springframework\spring-core\5.3.22\spring-core-5.3.22.jar;D:\.m2\repository\org\springframework\spring-jcl\5.3.22\spring-jcl-5.3.22.jar;D:\.m2\repository\org\springframework\boot\spring-boot-starter-web\2.7.3\spring-boot-starter-web-2.7.3.jar;D:\.m2\repository\org\springframework\boot\spring-boot-starter-json\2.7.3\spring-boot-starter-json-2.7.3.jar;D:\.m2\repository\com\fasterxml\jackson\core\jackson-databind\2.13.3\jackson-databind-2.13.3.jar;D:\.m2\repository\com\fasterxml\jackson\core\jackson-annotations\2.13.3\jackson-annotations-2.13.3.jar;D:\.m2\repository\com\fasterxml\jackson\core\jackson-core\2.13.3\jackson-core-2.13.3.jar;D:\.m2\repository\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.13.3\jackson-datatype-jdk8-2.13.3.jar;D:\.m2\repository\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.13.3\jackson-datatype-jsr310-2.13.3.jar;D:\.m2\repository\com\fasterxml\jackson\module\jackson-module-parameter-names\2.13.3\jackson-module-parameter-names-2.13.3.jar;D:\.m2\repository\org\springframework\boot\spring-boot-starter-tomcat\2.7.3\spring-boot-starter-tomcat-2.7.3.jar;D:\.m2\repository\org\apache\tomcat\embed\tomcat-embed-core\9.0.65\tomcat-embed-core-9.0.65.jar;D:\.m2\repository\org\apache\tomcat\embed\tomcat-embed-el\9.0.65\tomcat-embed-el-9.0.65.jar;D:\.m2\repository\org\apache\tomcat\embed\tomcat-embed-websocket\9.0.65\tomcat-embed-websocket-9.0.65.jar;D:\.m2\repository\org\springframework\spring-web\5.3.22\spring-web-5.3.22.jar;D:\.m2\repository\org\springframework\spring-webmvc\5.3.22\spring-webmvc-5.3.22.jar;D:\.m2\repository\org\springframework\spring-expression\5.3.22\spring-expression-5.3.22.jar com.example.demo.DemoApplication
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( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.7.3)
2022-09-08 10:24:27.311 INFO 23120 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication using Java 11.0.15 on sm15 with PID 23120 (C:\Users\mail2\Downloads\demo\target\classes started by mail2 in C:\Users\mail2\Downloads\demo)
2022-09-08 10:24:27.311 INFO 23120 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to 1 default profile: "default"
2022-09-08 10:24:28.185 INFO 23120 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
2022-09-08 10:24:28.253 INFO 23120 --- [ main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 50 ms. Found 1 JPA repository interfaces.
2022-09-08 10:24:29.204 INFO 23120 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2022-09-08 10:24:29.219 INFO 23120 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2022-09-08 10:24:29.219 INFO 23120 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.65]
2022-09-08 10:24:29.348 INFO 23120 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2022-09-08 10:24:29.348 INFO 23120 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1933 ms
2022-09-08 10:24:29.580 INFO 23120 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2022-09-08 10:24:29.919 INFO 23120 --- [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
2022-09-08 10:24:30.033 INFO 23120 --- [ main] o.hibernate.jpa.internal.util.LogHelper : HHH000204: Processing PersistenceUnitInfo [name: default]
2022-09-08 10:24:30.103 INFO 23120 --- [ main] org.hibernate.Version : HHH000412: Hibernate ORM core version 5.6.10.Final
2022-09-08 10:24:30.309 INFO 23120 --- [ main] o.hibernate.annotations.common.Version : HCANN000001: Hibernate Commons Annotations {5.1.2.Final}
2022-09-08 10:24:30.471 INFO 23120 --- [ main] org.hibernate.dialect.Dialect : HHH000400: Using dialect: org.hibernate.dialect.H2Dialect
Hibernate: drop table if exists student CASCADE
Hibernate: create table student (student_id integer generated by default as identity, grade varchar(255), name varchar(255), primary key (student_id))
2022-09-08 10:24:31.144 INFO 23120 --- [ main] o.h.e.t.j.p.i.JtaPlatformInitiator : HHH000490: Using JtaPlatform implementation: [org.hibernate.engine.transaction.jta.platform.internal.NoJtaPlatform]
2022-09-08 10:24:31.167 INFO 23120 --- [ main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
2022-09-08 10:24:31.569 WARN 23120 --- [ main] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
2022-09-08 10:24:32.007 INFO 23120 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2022-09-08 10:24:32.023 INFO 23120 --- [ main] com.example.demo.DemoApplication : Started DemoApplication in 5.357 seconds (JVM running for 6.004)
2022-09-08 10:25:00.352 INFO 23120 --- [nio-8080-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2022-09-08 10:25:00.352 INFO 23120 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2022-09-08 10:25:00.353 INFO 23120 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Completed initialization in 1 ms
Hibernate: insert into student (student_id, grade, name) values (default, ?, ?)
Source Code:
https://github.com/NumeroUnoDeveloper/Spring-Boot-Rest-Service
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