如何在 Spring REST 控制器中访问纯 JSON 主体？

Question

有以下代码：

@RequestMapping(value = "/greeting", method = POST, consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
@ResponseBody
public String greetingJson(@RequestBody String json) {
    System.out.println("json = " + json); // TODO json is null... how to retrieve plain json body?
    return "Hello World!";
}

尽管 JSON 在正文中发送，但字符串

json

参数始终为

null

。

注意，我不需要自动类型转换，我只想要纯 JSON 结果。

这例如有效：

@RequestMapping(value = "/greeting", method = POST, consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
@ResponseBody
public String greetingJson(@RequestBody User user) {
    return String.format("Hello %s!", user);
}

也许我可以使用

ServletRequest

或

InputStream

作为参数来检索实际的身体，但我想知道是否有更简单的方法？

Answer 1

到目前为止我发现的最好方法是：

@RequestMapping(value = "/greeting", method = POST, consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
@ResponseBody
public String greetingJson(HttpEntity<String> httpEntity) {
    String json = httpEntity.getBody();
    // json contains the plain json string

让我知道是否还有其他选择。

Answer 2

你可以直接使用

@RequestBody String pBody

Answer 3

只有 HttpServletRequest 对我有用。 HttpEntity 给出了空字符串。

import java.io.IOException;
import javax.servlet.http.HttpServletRequest;
import org.apache.commons.io.IOUtils;

@RequestMapping(value = "/greeting", method = POST, consumes = APPLICATION_JSON_VALUE, produces = APPLICATION_JSON_VALUE)
@ResponseBody
public String greetingJson(HttpServletRequest request) throws IOException {
    final String json = IOUtils.toString(request.getInputStream(), StandardCharsets.UTF_8);
    System.out.println("json = " + json);
    return "Hello World!";
}

Answer 4

对我有用的最简单方法是

@RequestMapping(value = "/greeting", method = POST, consumes = MediaType.ALL_VALUE, produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
@ResponseBody
public String greetingJson(String raw) {
    System.out.println("json = " + raw);
    return "OK";
}

Answer 5

如果您有数十种方法需要以 JSON 形式获取 HTTP 正文并将其转换为自定义数据类型，那么这是在框架上实现支持的更好方法

public static class Data {
    private String foo;
    private String bar;
}

//convert http body to Data object.
//you can also use String parameter type to get the raw json text.
@RequestMapping(value = "/greeting")
@ResponseBody
public String greetingJson(@JsonBody Data data) {
    System.out.println(data);
    return "OK";
}

请注意，我们使用用户定义的注释

@JsonBody

。

// define custom annotation
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
public @interface JsonBody {
    String encoding() default "utf-8";
}

//annotation processor for JsonBody 
@Slf4j
public class JsonBodyArgumentResolver implements HandlerMethodArgumentResolver {

    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.getParameterAnnotation(JsonBody.class) != null;
    }

    @Override
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest,
                              WebDataBinderFactory binderFactory) throws Exception {
        JsonBody annotation = parameter.getParameterAnnotation(JsonBody.class);
        assert annotation != null;
        ServletRequest servletRequest = webRequest.getNativeRequest(ServletRequest.class);
        if (servletRequest == null) {
            throw new Exception("can not get ServletRequest from NativeWebRequest");
        }
        String copy = StreamUtils.copyToString(servletRequest.getInputStream(), Charset.forName(annotation.encoding()));
        return new Gson().fromJson(copy, parameter.getGenericParameterType());
    }
}

// register the annotation processor
@Component
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
        resolvers.add(new JsonBodyArgumentResolver());
    }
}

Answer 6

从 4.1 开始，您现在可以使用

RequestEntity<String> requestEntity

并通过

requestEntity.getBody()

访问正文

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/http/RequestEntity.html