Spring MVC 数据绑定的扩展

Spring MVC 数据绑定的扩展

Spring MVC经过三个版本，功能已经改进和完善了很多。尤其是2.5以来采用的Annotation的参数绑定，极大的方便了开发，3.0对其进行更进一步的完善。对于一些特殊的前台框架，传到后台的不是普通的request中的参数，而是request流中的xml格式，这时就不能采用SpringMVC自带的参数绑定方法。这时候考虑是否能扩展一下。SpringMVC默认使用的是AnnotationMethodHandlerAdapter.java，可以修改这个类来实现扩展。关键位置在如下方法中：protected ModelAndView invokeHandlerMethod(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {     ServletHandlerMethodResolver methodResolver= getMethodResolver(handler);     Method handlerMethod = methodResolver.resolveHandlerMethod(request);     ServletHandlerMethodInvoker methodInvoker=new ServletHandlerMethodInvoker(methodResolver);     ServletWebRequest webRequest = new ServletWebRequest(request, response);     ExtendedModelMap implicitModel = new BindingAwareModelMap();     Object result=methodInvoker.invokeHandlerMethod(handlerMethod,handler,webRequest, implicitModel);     ModelAndView mav=methodInvoker.getModelAndView(handlerMethod,handler.getClass(),result, implicitModel, webRequest);    methodInvoker.updateModelAttributes(handler,(mav!=null?mav.getModel():null),implicitModel,webRequest);     return mav;    }蓝色位置是关键点，ServletHandlerMethodInvoker.java是内部类，继承自HandlerMethodInvoker.java，invokeHandlerMethod方法需要扩展，继续跟踪这个方法，发现是HandlerMethodInvoker.java这个类的方法，这个方法中的关键方法是resolveHandlerArguments()，关键部分如下if (RequestParam.class.isInstance(paramAnn)) { RequestParam requestParam = (RequestParam) paramAnn; paramName = requestParam.value(); required = requestParam.required(); defaultValue = parseDefaultValueAttribute(requestParam.defaultValue()); annotationsFound++; } else if (RequestHeader.class.isInstance(paramAnn)) { RequestHeader requestHeader = (RequestHeader) paramAnn; headerName = requestHeader.value(); required = requestHeader.required(); defaultValue = parseDefaultValueAttribute(requestHeader.defaultValue()); annotationsFound++; }到此扩展的话需要添加自己的类型，如RequestParamExt，添加在后面，模仿如下： else if (RequestParamExt.class.isInstance(paramAnn)) { RequestParamExtrequestParam = (RequestParamExt) paramAnn; paramName = requestParam.value(); defaultValue = parseDefaultValueAttribute(requestParam.defaultValue()); miType = requestParam.type(); annotationsFound++; }在else if (paramName != null) { args[i] = resolveRequestParam(paramName, required, defaultValue, methodParam, webRequest, handler); }这个方法上面添加扩展逻辑： if(!RequestParamExt.TYPE_NONE.equals(miType)){ if(null == platformRequest){ HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class); platformRequest = new PlatformRequest((HttpServletRequest)request, "utf-8"); platformRequest.receiveData(); } if(RequestParamExt.TYPE_PLATFORMREQUEST.equals(miType)){     args[i] = platformRequest; } else if(RequestParamExt.TYPE_STR.equals(miType)){ args[i] = resolveRequestStrParamExt(platformRequest, methodParam); }else{ args[i] = resolveRequestParamExt(miType,platformRequest,paramName, defaultValue, methodParam, webRequest, handler); } }两个resolveRequest*Ext方法如下： protected Object resolveRequestStrParamExt(PlatformRequest platformRequest, MethodParameter methodParam){ VariableList inVl = platformRequest.getVariableList(); String paraName = methodParam.getParameterName(); return inVl.getValueAsObject(paraName); } protected Object resolveRequestParamExt(String miType,PlatformRequest platformRequest, String paramName, String defaultValue,MethodParameter methodParam,NativeWebRequest webRequest, Object handler)throws Exception{ if(StringUtils.isBlank(paramName)){ paramName = defaultValue; } Class<?> paramType = methodParam.getParameterType(); DatasetList inDl = platformRequest.getDatasetList(); VariableList inVl = platformRequest.getVariableList(); if(RequestParamExt.TYPE_DS.equals(miType)){//绑定的关键过程 Dataset ds = inDl.getDataset(paramName); Object vo = paramType.newInstance(); MiPDataBinder dataBinder = new MiPDataBinder(vo, false);     dataBinder.bind(inVl);     return dataBinder.getTarget(); } }同时还需要一个annotation的定义：示例如下：package com.company.springext.web.bind.annotation;import java.lang.annotation.Documented;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;&#64;Target(ElementType.PARAMETER)&#64;Retention(RetentionPolicy.RUNTIME)&#64;Documentedpublic &#64;interface RequestParamExt {    public static final String TYPE_NONE            = "none";    public static final String TYPE_DS              = "ds";    public static final String TYPE_VL              = "vl";    public static final String TYPE_STR             = "string";   String type() default TYPE_NONE; String value() default "";    String defaultValue() default "ds";}最后是修改Spring配置：<bean class="com.company.springext.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapterExt">  </bean>  到此就实现了自定义格式的数据绑定。对于特定格式的输出，如果需要自定义的话，同样需要修改AnnotationMethodHandlerAdapterExt.java这个类，关键位置在getModelAndView()方法。在如下位置：} else if (AnnotationUtils.findAnnotation(handlerMethod, ResponseBody.class) != null) {            handleResponseBody(returnValue, webRequest);            return null;        }添加自己的扩展方法：else if (AnnotationUtils.findAnnotation(handlerMethod, ResponseBodyExt.class) != null) {                ResponseBodyExt bodyMi = AnnotationUtils.findAnnotation(handlerMethod, ResponseBodyExt.class);                handleResponseBodyExt(returnValue, webRequest, bodyMi);                return null;            }定义handleResponseBodyExt方法： private void handleResponseBodyExt(Object returnValue, ServletWebRequest webRequest, ResponseBodyMI bodyMi) throws Exception {            HttpServletResponse servletResponse = (HttpServletResponse) webRequest.getNativeResponse();            writeWithExtConverters(returnValue, servletResponse, bodyMi);        }writeWithExtConverters()方法如下： private void writeWithExtConverters(Object returnValue, HttpServletResponse response, ResponseBodyMI bodyMi) throws Exception {                 convertToXML(...);        };使用方式如下：    &#64;RequestMapping(value="/getContractList")    &#64;ResponseBodyExt(isCheck=true, resultType="sql", sqlColumns="ID,TUREID")     public Page<Contract> getContractList(&#64;RequestParamExt(value = "ds_search", type = "ds") Contract cp) throws Exception { Page<Contract> page = method1(); return page; }QQ:24889356