在Spring Boot中整合Katharsis,来快速开发JSON API的Web应用

1 简介

我们进行Web API开发的时候,经常会使用Json格式的消息体,而Json格式非常灵活,不同的人会有不同的设计风格和实现,而JSON API提供了一套标准。但它并不提供直接实现。

Katharsis是JSON API的Java实现,使用它可以快速开发出Json based的Web接口,还能快速的整合到Spring中。今天我们就来试试如何在Spring Boot中使用Katharsis。

2 整合过程

2.1 添加依赖

我们在Spring Boot中添加依赖如下,包括常规的starter、jpa和h2,而整合Katharsis只需要katharsis-spring即可。

<dependencies>
 <dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-web</artifactId>
 </dependency>
 <dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-data-jpa</artifactId>
 </dependency>
 <dependency>
 <groupId>com.h2database</groupId>
 <artifactId>h2</artifactId>
 </dependency>
 <dependency>
 <groupId>io.katharsis</groupId>
 <artifactId>katharsis-spring</artifactId>
 <version>3.0.2</version>
 </dependency>
</dependencies>

2.2 Entity类

我们定义两个Entity,一个是学生,一个是教室,而教室对象会包含多个学生。

学生:

@JsonApiResource(type = "students")
@Entity
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class Student {
 @JsonApiId
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
 private Long id;
 private String name;
}

教室:

@JsonApiResource(type = "classrooms")
@Entity
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class Classroom {
 @JsonApiId
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
 private Long id;
 private String name;
 @ManyToMany(fetch = FetchType.EAGER)
 @JoinTable(name = "classrooms_students", joinColumns = @JoinColumn(name = "classroom_id", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name = "student_id", referencedColumnName = "id"))
 @JsonApiRelation(serialize= SerializeType.EAGER)
 private Set<Student> students;
}

注解JsonApiResource这个会指定资源名称,这个会影响api的URL,注解JsonApiId则指定资源的id。

2.3 资源操作类

Katharsis使用ResourceRepository来对资源进行增删改查操作,这个跟数据库的增删改查类似,但属于更高一层。抽象到资源RESTful的资源层面,然后再调用数据库的Repository来操作,这里统一实现ResourceRepositoryV2接口。

@Component
public class StudentResourceRepository implements ResourceRepositoryV2<Student, Long> {
 private final StudentRepository studentRepository;
 public StudentResourceRepository(StudentRepository studentRepository) {
 this.studentRepository = studentRepository;
 }
 @Override
 public Student findOne(Long id, QuerySpec querySpec) {
 Optional<Student> student = studentRepository.findById(id);
 return student.orElse(null);
 }
 @Override
 public ResourceList<Student> findAll(QuerySpec querySpec) {
 return querySpec.apply(studentRepository.findAll());
 }
 @Override
 public ResourceList<Student> findAll(Iterable<Long> ids, QuerySpec querySpec) {
 return querySpec.apply(studentRepository.findAllById(ids));
 }
 @Override
 public <S extends Student> S save(S entity) {
 return studentRepository.save(entity);
 }
 @Override
 public void delete(Long id) {
 studentRepository.deleteById(id);
 }
 @Override
 public Class<Student> getResourceClass() {
 return Student.class;
 }
 @Override
 public <S extends Student> S create(S entity) {
 return save(entity);
 }
}

而数据库方面我们使用JPA实现即可:

public interface StudentRepository extends JpaRepository<Student, Long> {
}

上面的代码是针对Student资源类型的,对Classroom类似,就不把代码列出来了。

2.4 配置

为了使用Katharsis,我们需要在配置中引入KatharsisConfigV3,我们直接在Spring Boot启动类中引入即可:

@SpringBootApplication
@Import(KatharsisConfigV3.class)
public class KatharsisExample {
 public static void main(String[] args) {
 SpringApplication.run(KatharsisExample.class, args);
 }
}

Spring Boot的配置文件如下:

server.port=8080
server.servlet.context-path=/
katharsis.domainName=https://www.pkslow.com
katharsis.pathPrefix=/api/katharsis
spring.datasource.url = jdbc:h2:mem:springKatharsis;DB_CLOSE_DELAY=-1
spring.datasource.username = sa
spring.datasource.password =
spring.jpa.show-sql = true
spring.jpa.hibernate.ddl-auto = create-drop
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.H2Dialect
spring.jpa.properties.hibernate.globally_quoted_identifiers=true

katharsis.pathPrefix是URL前缀,而katharsis.domainName会影响Self Link等返回。

2.5 初始化数据

为了方便测试,初始化一些数据进行查询:

@Component
public class InitData {
 private final ClassroomRepository classroomRepository;
 private final StudentRepository studentRepository;
 public InitData(ClassroomRepository classroomRepository, StudentRepository studentRepository) {
 this.classroomRepository = classroomRepository;
 this.studentRepository = studentRepository;
 }
 @PostConstruct
 private void setupData() {
 Set<Student> students = new HashSet<>();
 Student student = Student.builder().name("Larry Deng").build();
 students.add(student);
 studentRepository.save(student);
 student = Student.builder().name("Eason").build();
 students.add(student);
 studentRepository.save(student);
 student = Student.builder().name("JJ Lin").build();
 students.add(student);
 studentRepository.save(student);
 Classroom classroom = Classroom.builder().name("Classroom No.1").students(students)
 .build();
 classroomRepository.save(classroom);
 }
}

至此则整合完毕了。

3 测试

整合完后启动,就可以用curl或Postman开始测试了:

查询一个student:

$ curl http://localhost:8080/api/katharsis/students/1 | jq .
 % Total % Received % Xferd Average Speed Time Time Time Current
 Dload Upload Total Spent Left Speed
100 139 0 139 0 0 9828 0 --:--:-- --:--:-- --:--:-- 23166
{
 "data": {
 "id": "1",
 "type": "students",
 "attributes": {
 "name": "Larry Deng"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/1"
 }
 }
}

查询多个student:

$ curl http://localhost:8080/api/katharsis/students | jq .
 % Total % Received % Xferd Average Speed Time Time Time Current
 Dload Upload Total Spent Left Speed
100 429 0 429 0 0 3633 0 --:--:-- --:--:-- --:--:-- 3830
{
 "data": [
 {
 "id": "1",
 "type": "students",
 "attributes": {
 "name": "Larry Deng"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/1"
 }
 },
 {
 "id": "2",
 "type": "students",
 "attributes": {
 "name": "Eason"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/2"
 }
 },
 {
 "id": "3",
 "type": "students",
 "attributes": {
 "name": "JJ Lin"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/3"
 }
 }
 ],
 "meta": {
 "totalResourceCount": null
 }
}

查询一个教室:

$ curl http://localhost:8080/api/katharsis/classrooms/4 | jq .
 % Total % Received % Xferd Average Speed Time Time Time Current
 Dload Upload Total Spent Left Speed
100 834 0 834 0 0 62462 0 --:--:-- --:--:-- --:--:-- 116k
{
 "data": {
 "id": "4",
 "type": "classrooms",
 "attributes": {
 "name": "Classroom No.1"
 },
 "relationships": {
 "students": {
 "data": [
 {
 "id": "3",
 "type": "students"
 },
 {
 "id": "2",
 "type": "students"
 },
 {
 "id": "1",
 "type": "students"
 }
 ],
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/classrooms/4/relationships/students",
 "related": "https://www.pkslow.com/api/katharsis/classrooms/4/students"
 }
 }
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/classrooms/4"
 }
 },
 "included": [
 {
 "id": "1",
 "type": "students",
 "attributes": {
 "name": "Larry Deng"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/1"
 }
 },
 {
 "id": "2",
 "type": "students",
 "attributes": {
 "name": "Eason"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/2"
 }
 },
 {
 "id": "3",
 "type": "students",
 "attributes": {
 "name": "JJ Lin"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/3"
 }
 }
 ]
}

新增一个学生:

$ curl --header "Content-Type: application/json" --request POST --data '{
 "data": {
 "type": "students",
 "attributes": {
 "name": "Justin"
 }
 }
}' http://localhost:8080/api/katharsis/students | jq .
 % Total % Received % Xferd Average Speed Time Time Time Current
 Dload Upload Total Spent Left Speed
100 249 0 135 100 114 11202 9459 --:--:-- --:--:-- --:--:-- 41500
{
 "data": {
 "id": "6",
 "type": "students",
 "attributes": {
 "name": "Justin"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/6"
 }
 }
}

修改:

$ curl --header "Content-Type: application/json" --request PATCH --data '{
 "data": {
 "id":"6",
 "type": "students",
 "attributes": {
 "name": "Justin Wu"
 }
 }
}' http://localhost:8080/api/katharsis/students/6 | jq .
 % Total % Received % Xferd Average Speed Time Time Time Current
 Dload Upload Total Spent Left Speed
100 273 0 138 100 135 4425 4329 --:--:-- --:--:-- --:--:-- 10920
{
 "data": {
 "id": "6",
 "type": "students",
 "attributes": {
 "name": "Justin Wu"
 },
 "links": {
 "self": "https://www.pkslow.com/api/katharsis/students/6"
 }
 }
}

删除:

$ curl --header "Content-Type: application/json" --request DELETE --data '{
 "data": {
 "id":"6",
 "type": "students",
 "attributes": {
 "name": "Justin Wu"
 }
 }
}' http://localhost:8080/api/katharsis/students/6 | jq .

至此,我们已经覆盖了增删改查操作了。而我们在代码中并没有去写我们之前常写的Controller,却可以访问对应接口。因为Katharsis默认已经帮我们实现了,可以查看类:io.katharsis.core.internal.dispatcher.ControllerRegistry

4 代码

代码请看GitHub: https://github.com/LarryDpk/pkslow-samples

作者:南瓜慢说原文地址:https://www.cnblogs.com/larrydpk/p/17090507.html

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