Struts2源码分析之ParametersInterceptor拦截器

@Override
public String doIntercept(ActionInvocation invocation) throws Exception {
Object action = invocation.getAction();//获取当前执行的Action对象
if (!(action instanceof NoParameters)) {//判断Action是否实现了NoParameters接口，实现该接口表示该Action没有任何请求参数
ActionContext ac = invocation.getInvocationContext();//获取ActionContext对象
final Map<String, Object> parameters = retrieveParameters(ac);//获取请求参数Map
//省略...
if (parameters != null) {//如果请求参数不为null
Map<String, Object> contextMap = ac.getContextMap();//获取ActionContext内部的context Map，即OgnlContext对象
try {
//省略...
ValueStack stack = ac.getValueStack();//获取值栈
setParameters(action, stack, parameters);//为值栈设置参数
} finally {
//省略...
}
}
}
return invocation.invoke();//调用下一个拦截器
}

protected void setParameters(Object action, ValueStack stack, final Map<String, Object> parameters) {
ParameterNameAware parameterNameAware = (action instanceof ParameterNameAware)
? (ParameterNameAware) action : null;//判断Action有无实现ParameterNameAware接口
Map<String, Object> params;
Map<String, Object> acceptableParameters;//合法参数集合
//判断参数设置是否有序，ordered默认为false，即无序
if (ordered) {
params = new TreeMap<String, Object>(getOrderedComparator());//如果有序则要获取比较器
acceptableParameters = new TreeMap<String, Object>(getOrderedComparator());
params.putAll(parameters);
} else {
params = new TreeMap<String, Object>(parameters);
acceptableParameters = new TreeMap<String, Object>();
}
//迭代请求参数
for (Map.Entry<String, Object> entry : params.entrySet()) {
String name = entry.getKey();
//判断参数是否合法，如果Action实现了ParameterNameAware则acceptableName(name)返回true且parameterNameAware.acceptableParameterName(name)
//也返回true该参数才是合法的；如果Action没有实现ParameterNameAware则参数是否合法由acceptableName(name)方法决定
boolean acceptableName = acceptableName(name) && (parameterNameAware == null || parameterNameAware.acceptableParameterName(name));
//如果参数合法
if (acceptableName) {
acceptableParameters.put(name, entry.getValue());//把合法参数添加到合法参数集合中
}
}
ValueStack newStack = valueStackFactory.createValueStack(stack);
//省略...
for (Map.Entry<String, Object> entry : acceptableParameters.entrySet()) {//迭代合法参数
String name = entry.getKey();//参数名
Object value = entry.getValue();//参数值
try {
newStack.setValue(name, value);//将该参数设置到ValueStack中
} catch (RuntimeException e) {
//省略...
}
}
//省略...
//看该方法的名称是将合法参数添加到ActionContext中，但在该拦截器中，该方法为空实现，无任何代码
//该方法被声明为protected，即子类可以覆盖该方法以改变行为
addParametersToContext(ActionContext.getContext(), acceptableParameters);
}

protected boolean acceptableName(String name) {
//调用isAccepted与isExcluded方法判断
if (isAccepted(name) && !isExcluded(name)) {
return true;
}
return false;
}

protected boolean isAccepted(String paramName) {
if (!this.acceptParams.isEmpty()) {
for (Pattern pattern : acceptParams) {
Matcher matcher = pattern.matcher(paramName);
if (matcher.matches()) {
return true;
}
}
return false;
} else
return acceptedPattern.matcher(paramName).matches();
}
protected boolean isExcluded(String paramName) {
if (!this.excludeParams.isEmpty()) {
for (Pattern pattern : excludeParams) {
Matcher matcher = pattern.matcher(paramName);
if (matcher.matches()) {
return true;
}
}
}
return false;
}