struts2常见的result类型的用法

这个是官方文档的上面对result类型的描述



我自己又找了一个中文的：



本文重点分享一下几个常用的result类型之后的原理：

一：dispatcher

从源码分析：

public void doExecute(String finalLocation, ActionInvocation invocation) throws Exception {
if (LOG.isDebugEnabled()) {
LOG.debug("Forwarding to location " + finalLocation);
}

PageContext pageContext = ServletActionContext.getPageContext();

if (pageContext != null) {
pageContext.include(finalLocation);
} else {
HttpServletRequest request = ServletActionContext.getRequest();
HttpServletResponse response = ServletActionContext.getResponse();
RequestDispatcher dispatcher = request.getRequestDispatcher(finalLocation);

//add parameters passed on the location to #parameters
// see WW-2120
if (StringUtils.isNotEmpty(finalLocation) && finalLocation.indexOf("?") > 0) {
String queryString = finalLocation.substring(finalLocation.indexOf("?") + 1);
Map<String, Object> parameters = getParameters(invocation);
Map<String, Object> queryParams = urlHelper.parseQueryString(queryString, true);
if (queryParams != null && !queryParams.isEmpty())
parameters.putAll(queryParams);
}

// if the view doesn't exist, let's do a 404
if (dispatcher == null) {
response.sendError(404, "result '" + finalLocation + "' not found");
return;
}

//if we are inside an action tag, we always need to do an include
Boolean insideActionTag = (Boolean) ObjectUtils.defaultIfNull(request.getAttribute(StrutsStatics.STRUTS_ACTION_TAG_INVOCATION), Boolean.FALSE);

// If we're included, then include the view
// Otherwise do forward
// This allow the page to, for example, set content type
if (!insideActionTag && !response.isCommitted() && (request.getAttribute("javax.servlet.include.servlet_path") == null)) {
request.setAttribute("struts.view_uri", finalLocation);
request.setAttribute("struts.request_uri", request.getRequestURI());

dispatcher.forward(request, response);
} else {
dispatcher.include(request, response);
}
}
}

结果又三个方向：

pageContext.include(finalLocation);

dispatcher.forward(request, response);

dispatcher.include(request, response);

而forward和include是差不多的。

 

二：chain

主要用于把相关的几个action连接起来，共同完成一个功能

public void execute(ActionInvocation invocation) throws Exception {
// if the finalNamespace wasn't explicitly defined, assume the current one
if (this.namespace == null) {
this.namespace = invocation.getProxy().getNamespace();
}

ValueStack stack = ActionContext.getContext().getValueStack();
String finalNamespace = TextParseUtil.translateVariables(namespace, stack);
String finalActionName = TextParseUtil.translateVariables(actionName, stack);
String finalMethodName = this.methodName != null
? TextParseUtil.translateVariables(this.methodName, stack)
: null;

if (isInChainHistory(finalNamespace, finalActionName, finalMethodName)) {
addToHistory(finalNamespace, finalActionName, finalMethodName);
throw new XWorkException("Infinite recursion detected: "
+ ActionChainResult.getChainHistory().toString());
}

if (ActionChainResult.getChainHistory().isEmpty() && invocation != null && invocation.getProxy() != null) {
addToHistory(finalNamespace, invocation.getProxy().getActionName(), invocation.getProxy().getMethod());
}
addToHistory(finalNamespace, finalActionName, finalMethodName);

HashMap<String, Object> extraContext = new HashMap<String, Object>();
extraContext.put(ActionContext.VALUE_STACK, ActionContext.getContext().getValueStack());
extraContext.put(ActionContext.PARAMETERS, ActionContext.getContext().getParameters());
extraContext.put(CHAIN_HISTORY, ActionChainResult.getChainHistory());

if (LOG.isDebugEnabled()) {
LOG.debug("Chaining to action " + finalActionName);
}

proxy = actionProxyFactory.createActionProxy(finalNamespace, finalActionName, finalMethodName, extraContext);
proxy.execute();
}

原理是根据action所在的namespace,action,method创建一个proxy代理，并且执行代理的过程。由于是在多个Action之间在同一个http请求中传递，所以可以共享其中的资源，这就是上面history的意思。根据以前context中的内容，共享给下面action.

三：redirect和redirection

由于都是一个类ServletRedirectResult中的方法，所以可以当做一个来考虑。

protected void doExecute(String finalLocation, ActionInvocation invocation) throws Exception {
ActionContext ctx = invocation.getInvocationContext();
HttpServletRequest request = (HttpServletRequest) ctx.get(ServletActionContext.HTTP_REQUEST);
HttpServletResponse response = (HttpServletResponse) ctx.get(ServletActionContext.HTTP_RESPONSE);

if (isPathUrl(finalLocation)) {
if (!finalLocation.startsWith("/")) {
ActionMapping mapping = actionMapper.getMapping(request, Dispatcher.getInstance().getConfigurationManager());
String namespace = null;
if (mapping != null) {
namespace = mapping.getNamespace();
}

if ((namespace != null) && (namespace.length() > 0) && (!"/".equals(namespace))) {
finalLocation = namespace + "/" + finalLocation;
} else {
finalLocation = "/" + finalLocation;
}
}

// if the URL's are relative to the servlet context, append the servlet context path
if (prependServletContext && (request.getContextPath() != null) && (request.getContextPath().length() > 0)) {
finalLocation = request.getContextPath() + finalLocation;
}

ResultConfig resultConfig = invocation.getProxy().getConfig().getResults().get(invocation.getResultCode());
if (resultConfig != null) {
Map<String, String> resultConfigParams = resultConfig.getParams();

for (Map.Entry<String, String> e : resultConfigParams.entrySet()) {
if (!getProhibitedResultParams().contains(e.getKey())) {
String potentialValue = e.getValue() == null ? "" : conditionalParse(e.getValue(), invocation);
if (!suppressEmptyParameters || ((potentialValue != null) && (potentialValue.length() > 0))) {
requestParameters.put(e.getKey(), potentialValue);
}
}
}
}

StringBuilder tmpLocation = new StringBuilder(finalLocation);
urlHelper.buildParametersString(requestParameters, tmpLocation, "&");

// add the anchor
if (anchor != null) {
tmpLocation.append('#').append(anchor);
}

finalLocation = response.encodeRedirectURL(tmpLocation.toString());
}

if (LOG.isDebugEnabled()) {
LOG.debug("Redirecting to finalLocation " + finalLocation);
}

sendRedirect(response, finalLocation);
}

方法的结果都是使用这个方法作为跳转：sendRedirect(response, finalLocation);重定向。

其他的velocity,freemarker,是整合了模板引擎，这个以前我竟然不知道，google了一下，发现还是很简单的。大家可以试着加到struts里面。