之前两篇博客springMVC源码分析--HandlerMethodReturnValueHandler返回值解析器(一)和springMVC源码分析--HandlerMethodReturnValueHandlerComposite返回值解析器集合(二)我们分别介绍了返回值处理器相关的东西,接下来我们选取一个简单的实现类ViewNameMethodReturnValueHandler来简单介绍一下返回值处理操作。
1、返回值为jsp页面地址
@RequestMapping(value = "input") public String inputProduct() { logger.info("inputProduct called"); return "jsp/ProductForm"; //对应jsp页面名称 }
2、ViewNameMethodReturnValueHandler中对返回值jsp/ProductForm的处理
实现代码如下:
@Override public void handleReturnValue(Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception { //判断是否是String类型 if (returnValue instanceof CharSequence) { //如果是将其设置为视图名称 String viewName = returnValue.toString(); mavContainer.setViewName(viewName); if (isRedirectViewName(viewName)) { mavContainer.setRedirectModelScenario(true); } } else if (returnValue != null){ // should not happen throw new UnsupportedOperationException("Unexpected return type: " + returnType.getParameterType().getName() + " in method: " + returnType.getMethod()); } }
这样就把返回值jsp/ProductForm作为视图名称放到ModelAndView中,这样就完成了返回值的处理操作。
ViewNameMethodReturnValueHandler完整源码如下,处理机制还是比较简单的。
//HandlerMethodReturnValueHandler的子类,主要就是Controller执行后返回的视图名称 public class ViewNameMethodReturnValueHandler implements HandlerMethodReturnValueHandler { private String[] redirectPatterns; //设置跳转链接的匹配方式 public void setRedirectPatterns(String... redirectPatterns) { this.redirectPatterns = redirectPatterns; } /** * The configured redirect patterns, if any. */ public String[] getRedirectPatterns() { return this.redirectPatterns; } @Override public boolean supportsReturnType(MethodParameter returnType) { Class<?> paramType = returnType.getParameterType(); return (void.class == paramType || CharSequence.class.isAssignableFrom(paramType)); } //实现逻辑还是比较简单的,就是设置ModelAndViewContainer的viewName视图名称 @Override public void handleReturnValue(Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception { if (returnValue instanceof CharSequence) { String viewName = returnValue.toString(); mavContainer.setViewName(viewName); if (isRedirectViewName(viewName)) { mavContainer.setRedirectModelScenario(true); } } else if (returnValue != null){ // should not happen throw new UnsupportedOperationException("Unexpected return type: " + returnType.getParameterType().getName() + " in method: " + returnType.getMethod()); } } //判断返回值是否是跳转链接,以redirect:开头 protected boolean isRedirectViewName(String viewName) { return (PatternMatchUtils.simpleMatch(this.redirectPatterns, viewName) || viewName.startsWith("redirect:")); } }