如何用Spring Web Client从HAL格式响应加载类字段并关联地址数据

1. 定义实体类 #

适配HAL格式的响应结构，借助Spring HATEOAS的RepresentationModel自动处理_links字段，同时定义业务实体：

Person实体类 #

import org.springframework.hateoas.RepresentationModel;
import java.util.List;

public class Person extends RepresentationModel<Person> {
    private Long id;
    private String name;
    private List<Address> addresses;

    // 构造器、getter、setter
    public Person() {}
    public Person(Long id, String name) {
        this.id = id;
        this.name = name;
    }

    // 自行补充getter和setter方法
}

Address实体类 #

public class Address {
    private String house;
    private String street;
    private String city;
    private String country;
    private String pincode;

    // 构造器、getter、setter
    public Address() {}

    // 自行补充getter和setter方法
}

HAL地址响应包装类 #

针对地址接口返回的_embedded结构，定义包装类解析数据：

import java.util.List;

public class AddressEmbeddedResponse {
    private List<Address> addresses;

    public List<Address> getAddresses() {
        return addresses;
    }

    public void setAddresses(List<Address> addresses) {
        this.addresses = addresses;
    }
}

注意：原地址响应中的_embaded是拼写错误，符合HAL规范的字段应为_embedded；若接口确实返回错误拼写，需给包装类字段添加@JsonProperty("_embaded")注解适配。

2. 配置WebClient实例 #

创建全局WebClient实例供业务调用：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.reactive.function.client.WebClient;

@Configuration
public class WebClientConfig {
    @Bean
    public WebClient webClient() {
        return WebClient.builder()
                .baseUrl("http://localhost:8080")
                .build();
    }
}

3. 编写业务调用逻辑 #

通过WebClient链式调用两个接口，解析HAL响应并关联数据：

import org.springframework.hateoas.Link;
import org.springframework.stereotype.Service;
import org.springframework.web.reactive.function.client.WebClient;
import reactor.core.publisher.Mono;

@Service
public class PersonService {
    private final WebClient webClient;

    public PersonService(WebClient webClient) {
        this.webClient = webClient;
    }

    public Mono<Person> getPersonWithAddresses(Long personId) {
        // 1. 调用人员接口获取HAL格式的Person数据
        return webClient.get()
                .uri("/person/{id}", personId)
                .retrieve()
                .bodyToMono(Person.class)
                // 2. 从Person的_links中提取addresses链接，调用地址接口
                .flatMap(person -> {
                    Link addressesLink = person.getLink("addresses")
                            .orElseThrow(() -> new RuntimeException("HAL响应中未找到addresses链接"));

                    return webClient.get()
                            .uri(addressesLink.getHref())
                            .retrieve()
                            .bodyToMono(AddressEmbeddedResponse.class)
                            // 3. 将地址列表设置到Person对象中
                            .map(embeddedResponse -> {
                                person.setAddresses(embeddedResponse.getAddresses());
                                return person;
                            });
                });
    }
}

4. 使用示例 #

在控制器中调用业务方法：

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import reactor.core.publisher.Mono;

@RestController
public class PersonController {
    private final PersonService personService;

    public PersonController(PersonService personService) {
        this.personService = personService;
    }

    @GetMapping("/person-with-addresses/{id}")
    public Mono<Person> getPersonWithAddresses(@PathVariable Long id) {
        return personService.getPersonWithAddresses(id);
    }
}

内容的提问来源于stack exchange，提问作者Rajesh Kumar