Spring Boot 项目中提供的 REST 接口往往需要封装状态或者其他附加的内容返回给客户端，如果每个接口都用一些工具类来处理很繁琐，会增加很多重复代码，还有可能漏掉导致客户端无法解析；用切面也可以实现，但是 SpringBoot 提供了处理的接口
- CustomResponse.java
import java.lang.annotation.*;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface CustomResponse {
}封装返回内容的实体
- CustomResponseContent.java
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class CustomResponseContent {
private Integer code;
private String status;
private Object data;
private String message;
}用于封装返回内容
- CustomResponseReturnValueHandler.java
public class CustomResponseReturnValueHandler implements HandlerMethodReturnValueHandler, AsyncHandlerMethodReturnValueHandler {
private static final ObjectMapper objectMapper;
static {
objectMapper = new ObjectMapper();
objectMapper.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);
objectMapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
}
@Override
public boolean isAsyncReturnValue(Object o, MethodParameter methodParameter) {
return supportsReturnType(methodParameter);
}
@Override
public boolean supportsReturnType(MethodParameter methodParameter) {
return methodParameter.getAnnotatedElement().getAnnotation(CustomResponse.class) != null;
}
@Override
public void handleReturnValue(Object data, MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer, NativeWebRequest nativeWebRequest) throws Exception {
modelAndViewContainer.setRequestHandled(true);
HttpServletResponse response = nativeWebRequest.getNativeResponse(HttpServletResponse.class);
response.setContentType(MediaType.APPLICATION_JSON_UTF8_VALUE);
String message = "操作成功";
String status = "success";
if ((data instanceof Boolean) && !((Boolean) data)) {
message = "操作失败";
status = "fail";
}
CustomResponseContent responseContent = CustomResponseContent.builder()
.code(response.getStatus())
.status(status)
.message(message)
.data(data)
.build();
response.getWriter()
.write(objectMapper.writeValueAsString(responseContent));
}
}将返回值处理器添加到应用中
- CustomWebMvcConfigurer.java
@Configuration
public class CustomWebMvcConfigurer implements WebMvcConfigurer {
@Override
public void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> handlers) {
handlers.add(new CustomResponseReturnValueHandler());
}
}- ProductController.java
@RestController
public class ProductController {
private static Map<Long, Product> productMap;
static {
productMap = Stream.of(
Product.builder().id(1L).name("product1").price(1L).build(),
Product.builder().id(2L).name("product2").price(2L).build(),
Product.builder().id(3L).name("product3").price(3L).build()
).collect(Collectors.toConcurrentMap(Product::getId, p -> p));
}
@GetMapping("/boolean")
@CustomResponse
public Boolean getBoolean(String booleanValue) {
return "true".equals(booleanValue);
}
@GetMapping("/product/{id}")
@CustomResponse
public Product getProduct(@PathVariable Long id) {
return productMap.get(id);
}
@GetMapping("/product")
public List<Product> getProducts() {
return new ArrayList<>(productMap.values());
}
}# 没有添加自定义返回值注解
curl localhost:8080/product
[{"id":1,"name":"product1","price":1},{"id":2,"name":"product2","price":2},{"id":3,"name":"product3","price":3}]%
# 添加了自定义返回值注解
curl localhost:8080/product/1
{"code":200,"status":"success","data":{"id":1,"name":"product1","price":1},"message":"操作成功"}%
# Boolean 值返回不容的状态
curl 'http://localhost:8080/boolean?value=true'
{"code":200,"status":"success","data":true,"message":"操作成功"}%
curl 'http://localhost:8080/boolean?value=false'
{"code":200,"status":"fail","data":false,"message":"操作失败"}%