网站简繁体转换.rar,盐城哪里帮助公司建网址,eclipse开发安卓app,龙岗中心城有学网站建设在我们进行Java的Web应用开发时#xff0c;如何写更少的代码#xff0c;做更多的事情。如何让开发更容易上手#xff0c;更专注于业务层面#xff0c;不需要太关心底层的实现。这里就分享一些我平时在搭建基础框架时候的一些心得体验。
统一处理返回值 在web应用中#x…在我们进行Java的Web应用开发时如何写更少的代码做更多的事情。如何让开发更容易上手更专注于业务层面不需要太关心底层的实现。这里就分享一些我平时在搭建基础框架时候的一些心得体验。
统一处理返回值 在web应用中通常前后端会定义一个统一的对象来封装返回值一般除了业务数据之外可能会包含一些请求相关的数据 例如以下这个对象
code来标识整个请求的结果msg用于返回错误信息data用于返回实际的业务数据。
{code: 0,msg: success,data: {}
}统一封装的好处就是前端可以使用统一的逻辑进行请求处理能够编写通用代码来处理返回值。
当然这也需要后端做一定的开发。通常我们都是直接写在代码里面手动去创建一个封装对象然后将数据set进去或者是封装类添加一些静态方法之类的。 在大部分情况下这些工作都是重复的。
ResponseBodyAdvice 的执行流程
今天介绍的这个接口 ResponseBodyAdvice, 这是由SpringMvc提供的一个接口在消息转换前处理返回值源码如下
public interface ResponseBodyAdviceT{boolean supports(MethodParameter returnType, Class? extends HttpMessageConverter? converterType);T beforeBodyWrite(T body, MethodParameter returnType, MediaType selectedContentType,Class? extends HttpMessageConverter? selectedConverterType,ServerHttpRequest request, ServerHttpResponse response);
}这个接口在返回值被消息转换器写回前端之前进行处理 大致处理流程如下 我们实现这个接口的代码主要在这个方法里被调用 RequestResponseBodyAdviceChain.processBody 可以看到这一段逻辑很简单
先执行ResponseBodyAdvice.supports看当前切面类是否支持如果支持再调用ResponseBodyAdvice.beforeBodyWrite方法并返回
返回值会被 HttpMessageConverter.write 接口在进行最终的转换例如转JSON然后写回前端
private T Object processBody(Nullable Object body, MethodParameter returnType, MediaType contentType,Class? extends HttpMessageConverter? converterType,ServerHttpRequest request, ServerHttpResponse response) {for (ResponseBodyAdvice? advice : getMatchingAdvice(returnType, ResponseBodyAdvice.class)) {if (advice.supports(returnType, converterType)) {body ((ResponseBodyAdviceT) advice).beforeBodyWrite((T) body, returnType,contentType, converterType, request, response);}}return body;
}ResponseBodyAdvice 的初始化
SpringMVC在初始化的时候 会调用RequestMappingHandlerAdapter.initControllerAdviceCache将ResponseBodyAdvice初始化到容器中
里面会调用ControllerAdviceBean.findAnnotatedBeans 获取所有带有 ControllerAdvice 注解的类
将所有实现了 ResponseBodyAdvice 接口的Bean放入requestResponseBodyAdviceBeans中 在之前介绍到的 getAdvice() 方法取得就是该对象。
//代码片段
public static ListControllerAdviceBean findAnnotatedBeans(ApplicationContext context) {return Arrays.stream(BeanFactoryUtils.beanNamesForTypeIncludingAncestors(context, Object.class)).filter(name - context.findAnnotationOnBean(name, ControllerAdvice.class) ! null).map(name - new ControllerAdviceBean(name, context)).collect(Collectors.toList());
}// 代码片段
for (ControllerAdviceBean adviceBean : adviceBeans) {Class? beanType adviceBean.getBeanType();if (beanType null) {throw new IllegalStateException(Unresolvable type for ControllerAdviceBean: adviceBean);}SetMethod attrMethods MethodIntrospector.selectMethods(beanType, MODEL_ATTRIBUTE_METHODS);if (!attrMethods.isEmpty()) {this.modelAttributeAdviceCache.put(adviceBean, attrMethods);}SetMethod binderMethods MethodIntrospector.selectMethods(beanType, INIT_BINDER_METHODS);if (!binderMethods.isEmpty()) {this.initBinderAdviceCache.put(adviceBean, binderMethods);}if (RequestBodyAdvice.class.isAssignableFrom(beanType)) {requestResponseBodyAdviceBeans.add(adviceBean);}if (ResponseBodyAdvice.class.isAssignableFrom(beanType)) {requestResponseBodyAdviceBeans.add(adviceBean);}
}了解到这些我们实现一个通用的返回值处理就很简单了 只需要实现 ResponseBodyAdvice 接口并且加上 ControllerAdvice 注解就可以了
这是我实现的一个统一封装返回值的实现 大家可以参考一下根据自己的业务需求来进行修改
package com.diamondfsd.fast.mvc.advice;import com.diamondfsd.fast.mvc.annotations.IgnoreAware;
import com.diamondfsd.fast.mvc.entity.FastResult;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;import java.lang.reflect.Method;
import java.util.Map;
import java.util.WeakHashMap;/*** 统一返回数据封装* author Diamond*/
ControllerAdvice
public class FastMvcResponseBodyAwareAdvice implements ResponseBodyAdviceObject {private final MapMethod, Boolean supportsCache new WeakHashMap();private final String [] basePackages;private ObjectMapper objectMapper new ObjectMapper();public FastMvcResponseBodyAwareAdvice(String [] basePackages) {this.basePackages basePackages;}Overridepublic boolean supports(MethodParameter returnType, Class? extends HttpMessageConverter? converterType) {if (supportsCache.containsKey(returnType.getMethod())) {return supportsCache.get(returnType.getMethod());}boolean isSupport getIsSupport(returnType);supportsCache.put(returnType.getMethod(), isSupport);return isSupport;}private boolean getIsSupport(MethodParameter returnType) {Class? declaringClass returnType.getMember().getDeclaringClass();IgnoreAware classIgnore declaringClass.getAnnotation(IgnoreAware.class);IgnoreAware methodIgnore returnType.getMethod().getAnnotation(IgnoreAware.class);if (classIgnore ! null || methodIgnore ! null || FastResult.class.equals(returnType.getGenericParameterType())) {return false;}for (int i 0; i basePackages.length; i) {if (declaringClass.getPackage().getName().startsWith(basePackages[i])) {return true;}}return false;}Overridepublic Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,Class? extends HttpMessageConverter? selectedConverterType, ServerHttpRequest request,ServerHttpResponse response) {FastResultObject result new FastResult();result.setData(body);if (returnType.getGenericParameterType().equals(String.class)) {try {response.getHeaders().set(Content-Type, application/json;charsetutf-8);return objectMapper.writeValueAsString(result);} catch (JsonProcessingException e) {e.printStackTrace();}}return result;}}
