java - Gson json对象错误IllegalStateException - Spring

Question

我正在尝试解析如下所示的 json 字符串，但当其余端点被命中时，我收到错误

读取 HTTP 消息失败:org.springframework.http.converter.HttpMessageNotReadableException:无法读取 JSON:java.lang.IllegalStateException:需要一个字符串，但在第 1 行第 2 列路径 $ 处为 BEGIN_OBJECT

{
  "resources": [
{
  "resourceType": "Car",
  "resourceId": "Car1"
},
{
  "resourceType": "Truck",
  "resourceId": "Truck1"
}
],
 "topics": [
   "some_data",
   "some_event"
]
}


@PostMapping(value = "/subscribe", consumes = MediaType.APPLICATION_JSON_VALUE)
public void create(@RequestBody String subscriptionRequest)
        throws Exception
{

    SubscriptionRequest request = new Gson().fromJson(subscriptionRequest, SubscriptionRequest.class); 

    if ( request.getResources().isEmpty() || request.getTopics().isEmpty() )
    {
        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(null);
    }
    other code ....
}


public class SubscriptionRequest
{
private List<Resources> resources = null;

private List<String> topics = null;

public SubscriptionRequest()
{
    super();
}

public List<Resources> getResources()
{
    return this.resources;
}

public void setResources(List<Resources> resources)
{
    this.resources = resources;
}

public List<String> getTopics()
{
    return this.topics;
}

public void setTopics(List<String> topics)
{
    this.topics = topics;
}

}

public class Resources {

    private List<Resource> resources = null;

    private int resourceId;

    public Resources() 
    {
        super();
    }

    public List<Resource> getResources() {
        return this.resources;
    }

    public void setResources(List<Resource> resources) {
        this.resources = resources;
    }
}

public class Resource {

    private String resourceType;

    private String resourceId;

    public Resource()
    {
        super();
    }

    public Resource(String resourceType, String resourceId) 
    {
        this.resourceType = resourceType;
        this.resourceId = resourceId;
    }

    public String getResourceType() 
    {
        return this.resourceType;
    }

    public void setResourceType(String resourceType) 
    {
        this.resourceType = resourceType;
    }

    public String getResourceId() 
    {
        return this.resourceId;
    }

    public void setResourceId(String resourceId) 
    {
        this.resourceId = resourceId;
    }
}

public class AppConfig extends WebMvcConfigurerAdapter
{
@Override
public void addCorsMappings(CorsRegistry registry) {
  registry.addMapping("/**")
      .allowedOrigins("*")
      .allowedMethods("POST", "GET",  "PUT", "OPTIONS", "DELETE")
      .allowedHeaders("X-Requested-With,Content-Type,Accept,Origin");
}

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    GsonHttpMessageConverter msgConverter = new GsonHttpMessageConverter();
    Gson gson = new GsonBuilder().setPrettyPrinting().create(); 
    msgConverter.setGson(gson);
    converters.add(msgConverter);
}
}   

Answer 1

通常，您会直接注入(inject)反序列化类型:

public void create(@RequestBody SubscriptionRequest subscriptionRequest)

Spring 负责反序列化它。在这里，您期望一个字符串，因此 Spring 尝试读取 JSON 输入(这是一个对象)，并将其反序列化为字符串，因此它会中断(期望一个字符串，但实际上是 BEGIN_OBJECT)。

尝试将整个输入用双引号引起来:

"{
  "resources": [
{
  "resourceType": "Car",
  "resourceId": "Car1"
},
{
  "resourceType": "Truck",
  "resourceId": "Truck1"
}
],
 "topics": [
   "some_data",
   "some_event"
]
}"

这可能会解决您眼前的问题，但这并不是您想要做的。相反，您可能应该将其留给 Spring，如上所述。