# 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 (opens new window)提供了一套标准。但它并不提供直接实现。
Katharsis (opens new window)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
References:
JSON API Implementations (opens new window)