ServletContext,ActionContext,ServletActionContext

梦里梦外; 2022-05-12 01:20 143阅读 0赞

**ServletContext**

*  ServletContext从他的package信息可以看出,它是标准的JavaEE WebApplication类库

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 <td>javax.servlet.ServletContext </td> 
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*  ServletContext提供了标准的Servlet运行环境,其实就是一些servlet和web container进行通信的方法

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 <td>public interface ServletContext { &nbsp;// Returns the URL prefix for the ServletContext. &nbsp;public String getServletContextName(); &nbsp;//Returns the ServletContext for the uri. &nbsp;public ServletContext getContext(String uri); &nbsp; &nbsp;//Returns the context-path for the web-application. &nbsp;public String getContextPath(); &nbsp; &nbsp;//Returns the real file path for the given uri. &nbsp;public String getRealPath(String uri); &nbsp; &nbsp;public RequestDispatcher getRequestDispatcher(String uri); &nbsp;public RequestDispatcher getNamedDispatcher(String servletName); </td> 
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 <td>public Object getAttribute(String name); public Enumeration getAttributeNames(); public void setAttribute(String name, Object value); public void removeAttribute(String name);</td> 
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*  注意:一个ServletContext对应一个命名空间的servlet( 比如/struts下的所有servlet),是被所有servlet共享的.

There is one context per “web application” per Java Virtual Machine.  
(A “web application” is a collection of servlets and content installed under a specific subset of the server’s URL namespace such as /catalog and possibly installed via a .war file.)

*  ServletContext被包含在ServletConfig对象中,ServletConfig对象通常被servlet或filter的init()方法读取

ServletConfig.getServletContext()  
filterconfig.getServletContext()  
  
  
ActionContext来源于Struts2 与 Struts1的本质不同.  
struts1时，由一个servlet (servlet org.apache.struts.action.ActionServlet)处理所有的\*.do  
struts2时，由一个filter(org.apache.struts2.dispatcher.FilterDispatcher)处理所有的请求  
struts1 仍旧属于servlet范畴,struts1 action 其本质仍是servlet.  
struts2 action 已经是普通的java bean了,已经跳出了servlet 框架  
ActionContext就是为了弥补strtus2 action跳出标准servlet框架而造成的和WEB环境失去联系的缺陷  
  
ActionContext的主要作用:

*  提供Web环境Context
 *  解决线程安全问题
 *  解决一些和其他框架或容器(siteMesh,webLogic)的兼容问题

分析ActionContext源码

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 <td>&nbsp;public class ActionContext implements Serializable { </td> 
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 <td>&nbsp; //ThreadLocal模式下的ActionContext实例,实现多线程下的线程安全/// &nbsp;&nbsp;&nbsp;&nbsp; static ThreadLocal actionContext = new ThreadLocal(); &nbsp;&nbsp;&nbsp; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; //Sets the action context for the current thread. &nbsp;&nbsp;&nbsp;&nbsp; public static void setContext(ActionContext context) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; actionContext.set(context); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; //Returns the ActionContext specific to the current thread. &nbsp;&nbsp;&nbsp;&nbsp; public static ActionContext getContext() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (ActionContext) actionContext.get(); &nbsp;&nbsp;&nbsp;&nbsp; }</td> 
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 <td>&nbsp;///定义放置”名/值对”的Map容器,这是ActionContext的主要功能///&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; Map&lt;String, Object&gt; context; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; // constractor&nbsp;&nbsp; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; // Creates a new ActionContext initialized with another context. &nbsp;&nbsp;&nbsp;&nbsp; public ActionContext(Map&lt;String, Object&gt; context) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; this.context = context; &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; public void setContextMap(Map&lt;String, Object&gt; contextMap) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; getContext().context = contextMap; &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public Map&lt;String, Object&gt; getContextMap() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return context; &nbsp;&nbsp;&nbsp;&nbsp; } //Returns a value that is stored in the current ActionContext by doing a lookup using the value’s key. &nbsp;&nbsp;&nbsp;&nbsp; public Object get(String key) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return context.get(key); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;//Stores a value in the current ActionContext. The value can be looked up using the key. &nbsp;&nbsp;&nbsp;&nbsp; public void put(String key, Object value) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; context.put(key, value); &nbsp;&nbsp;&nbsp;&nbsp; }</td> 
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 <td>///将各种功能属性放置入Map容器中/ &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; //action name, Constant for the name of the action being executed. &nbsp;&nbsp;&nbsp;&nbsp; public static final String ACTION_NAME = “com.opensymphony.xwork2.ActionContext.name”; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; // ognl value stack &nbsp;&nbsp;&nbsp;&nbsp; public static final String VALUE_STACK = ValueStack.VALUE_STACK; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; public static final String SESSION = “com.opensymphony.xwork2.ActionContext.session”; &nbsp;&nbsp;&nbsp;&nbsp; public static final String APPLICATION = “com.opensymphony.xwork2.ActionContext.application”; &nbsp;&nbsp;&nbsp;&nbsp; public static final String PARAMETERS = “com.opensymphony.xwork2.ActionContext.parameters”; &nbsp;&nbsp;&nbsp;&nbsp; public static final String LOCALE = “com.opensymphony.xwork2.ActionContext.locale”; &nbsp;&nbsp;&nbsp;&nbsp; public static final String TYPE_CONVERTER = “com.opensymphony.xwork2.ActionContext.typeConverter”; &nbsp;&nbsp;&nbsp;&nbsp; public static final String ACTION_INVOCATION = “com.opensymphony.xwork2.ActionContext.actionInvocation”; &nbsp;&nbsp;&nbsp;&nbsp; public static final String CONVERSION_ERRORS = “com.opensymphony.xwork2.ActionContext.conversionErrors”; &nbsp;&nbsp;&nbsp;&nbsp; public static final String CONTAINER = “com.opensymphony.xwork2.ActionContext.container”; &nbsp; &nbsp;// 各种Action主属性:ActionName, ActionInvocation(调用action的相关信息), ognl value stack/// &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; //Gets the name of the current Action. &nbsp;&nbsp;&nbsp;&nbsp; public String getName() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (String) get(ACTION_NAME); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; //Sets the name of the current Action in the ActionContext. &nbsp;&nbsp;&nbsp;&nbsp; public void setName(String name) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(ACTION_NAME, name); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; //Sets the action invocation (the execution state). &nbsp;&nbsp;&nbsp;&nbsp; public void setActionInvocation(ActionInvocation actionInvocation) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(ACTION_INVOCATION, actionInvocation); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public ActionInvocation getActionInvocation() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (ActionInvocation) get(ACTION_INVOCATION); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; // Sets the OGNL value stack. &nbsp;&nbsp;&nbsp;&nbsp; public void setValueStack(ValueStack stack) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(VALUE_STACK, stack); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; //Gets the OGNL value stack. &nbsp;&nbsp;&nbsp;&nbsp; public ValueStack getValueStack() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (ValueStack) get(VALUE_STACK); &nbsp;&nbsp;&nbsp;&nbsp; } 各种 request请求包含的内容 &nbsp;&nbsp;&nbsp;&nbsp; //Returns a Map of the HttpServletRequest parameters &nbsp;&nbsp;&nbsp;&nbsp; public Map&lt;String, Object&gt; getParameters() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (Map&lt;String, Object&gt;) get(PARAMETERS); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public void setParameters(Map&lt;String, Object&gt; parameters) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(PARAMETERS, parameters); &nbsp;&nbsp;&nbsp;&nbsp; }&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; public void setSession(Map&lt;String, Object&gt; session) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(SESSION, session); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public Map&lt;String, Object&gt; getSession() { &nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; return (Map&lt;String, Object&gt;) get(SESSION); &nbsp;&nbsp;&nbsp;&nbsp; }&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; public void setApplication(Map&lt;String, Object&gt; application) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(APPLICATION, application); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public Map&lt;String, Object&gt; getApplication() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (Map&lt;String, Object&gt;) get(APPLICATION); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; public void setConversionErrors(Map&lt;String, Object&gt; conversionErrors) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(CONVERSION_ERRORS, conversionErrors); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public Map&lt;String, Object&gt; getConversionErrors() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Map&lt;String, Object&gt; errors = (Map) get(CONVERSION_ERRORS); &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (errors == null) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; errors = new HashMap&lt;String, Object&gt;(); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; setConversionErrors(errors); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return errors; &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp; //Sets the Locale for the current action. &nbsp;&nbsp;&nbsp;&nbsp; public void setLocale(Locale locale) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(LOCALE, locale); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public Locale getLocale() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Locale locale = (Locale) get(LOCALE); &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (locale == null) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; locale = Locale.getDefault(); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; setLocale(locale); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return locale; &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public void setContainer(Container cont) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; put(CONTAINER, cont); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; public Container getContainer() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (Container) get(CONTAINER); &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; public &lt;T&gt; T getInstance(Class&lt;T&gt; type) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Container cont = getContainer(); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if (cont != null) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return cont.getInstance(type); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } else { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; throw new XWorkException(“Cannot find an initialized container for this request.”); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;&nbsp;&nbsp;&nbsp; } &nbsp;} </td> 
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ServletActionContext 其实是ActionContext的子类,其功能脱胎于ActionContext,对ActionContext的方法做了一定的包装,提供了更简便直观的方法

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 <td>&nbsp;public class ServletActionContext extends ActionContext implements StrutsStatics { </td> 
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 <td>/Servlet Context 提供了多种操作ActionContext的静态方法,使获得Web对象更方便 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //HTTP servlet request &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; public static void setRequest(HttpServletRequest request) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ActionContext.getContext().put(HTTP_REQUEST, request); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; public static HttpServletRequest getRequest() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (HttpServletRequest) ActionContext.getContext().get(HTTP_REQUEST); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //HTTP servlet response &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; public static void setResponse(HttpServletResponse response) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ActionContext.getContext().put(HTTP_RESPONSE, response); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; public static HttpServletResponse getResponse() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (HttpServletResponse) ActionContext.getContext().get(HTTP_RESPONSE); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //servlet context. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; public static ServletContext getServletContext() { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return (ServletContext) ActionContext.getContext().get(SERVLET_CONTEXT); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; public static void setServletContext(ServletContext servletContext) { &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ActionContext.getContext().put(SERVLET_CONTEXT, servletContext); &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } </td> 
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ServletContext,ActionContext,ServletActionContext

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