深海游弋的鱼 – 默默的点滴

mvn报错：No goals have been specified for this build

选择【Run As】-【Maven build】的时候，报：

[INFO] Scanning for projects…[INFO]
[INFO] BUILD FAILURE[INFO]
[INFO] Total time: 0.109s[INFO] Finished at: Wed Apr 13 11:04:20 CST 2011[INFO] Final Memory: 1M/4M[INFO]
ERROR] No goals have been specified for this build. You must specify a valid lifecycle phase or a goal in the format <plugin-prefix>:<goal> or <plugin-group-id>:<plugin-artifact-id>[:<plugin-version>]:<goal>. Available lifecycle phases are: validate, initialize, generate-sources, process-sources, generate-resources,
process-resources, compile, process-classes, generate-test-sources, process-test-sources, generate-test-resources, process-test-resources, test-compile, process-
test-classes, test, prepare-package, package, pre-integration-test, integration-test, post-integration-test, verify, install, deploy, pre-site, site, post-site, site-deploy,
pre-clean, clean, post-clean. -> [Help 1][ERROR] [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.[ERROR] Re-run Maven using the -X switch to enable full debug logging.[ERROR] [ERROR] For more information about the errors and possible solutions, please read the following articles:[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/NoGoalSpecifiedException

[INFO] Scanning for projects…[INFO]

[INFO] BUILD FAILURE[INFO]

[INFO] Total time: 0.109s[INFO] Finished at: Wed Apr 13 11:04:20 CST 2011[INFO] Final Memory: 1M/4M[INFO]

ERROR] No goals have been specified for this build. You must specify a valid lifecycle phase or a goal in the format <plugin-prefix>:<goal> or <plugin-group-id>:<plugin-artifact-id>[:<plugin-version>]:<goal>. Available lifecycle phases are: validate, initialize, generate-sources, process-sources, generate-resources,

process-resources, compile, process-classes, generate-test-sources, process-test-sources, generate-test-resources, process-test-resources, test-compile, process-

test-classes, test, prepare-package, package, pre-integration-test, integration-test, post-integration-test, verify, install, deploy, pre-site, site, post-site, site-deploy,

pre-clean, clean, post-clean. -> [Help 1][ERROR] [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.[ERROR] Re-run Maven using the -X switch to enable full debug logging.[ERROR] [ERROR] For more information about the errors and possible solutions, please read the following articles:[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/NoGoalSpecifiedException

eclipse安装的maven插件是m2eclipse，在控制台使用命令mvn compile并未报错。后在pom.xml文件<build>标签后面加上

<defaultGoal>compile</defaultGoal>

1	<defaultGoal>compile</defaultGoal>

即可。

其实使用命令行时就已经指定了phase，而使用m2eclipse的【Run As】-【Maven build】时并未为其指定goal或phase，所以才报这个错误。

Struts2使用execAndWait在Action中调用getText报告java.lang.NullPointerException

使用 Struts2 编写页面，遇到一个要长时间运行的接口，因此增加了一个execAndWait ，结果在 Action 中调用 getText的时候报告异常

java.lang.NullPointerException
at com.opensymphony.xwork2.util.LocalizedTextUtil.findText(LocalizedTextUtil.java:361)
at com.opensymphony.xwork2.TextProviderSupport.getText(TextProviderSupport.java:208)
at com.opensymphony.xwork2.TextProviderSupport.getText(TextProviderSupport.java:123)
at com.opensymphony.xwork2.ActionSupport.getText(ActionSupport.java:103)
at com.infy.action.LoginAction.execute(LoginAction.java:19)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:450)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:289)
at org.apache.struts2.interceptor.BackgroundProcess$1.run(BackgroundProcess.java:57)
at java.lang.Thread.run(Thread.java:662)

java.lang.NullPointerException

at com.opensymphony.xwork2.util.LocalizedTextUtil.findText(LocalizedTextUtil.java:361)

at com.opensymphony.xwork2.TextProviderSupport.getText(TextProviderSupport.java:208)

at com.opensymphony.xwork2.TextProviderSupport.getText(TextProviderSupport.java:123)

at com.opensymphony.xwork2.ActionSupport.getText(ActionSupport.java:103)

at com.infy.action.LoginAction.execute(LoginAction.java:19)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:450)

at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:289)

at org.apache.struts2.interceptor.BackgroundProcess$1.run(BackgroundProcess.java:57)

at java.lang.Thread.run(Thread.java:662)

查询了很多评论，最终找到原因跟解决方案，具体解释在 http://stackoverflow.com/questions/16692658/execandwait-interceptor-not-redirecting-to-success-page-after-waiting

execAndWait causes the action to be executed in a new thread.
Since ActionContext is ThreadLocal, the new thread will not get the values stored in the parent thread version of ActionContext. Every thread has a unique version of ActionContext
getText() will throw a NPE when it tries to execute in the new thread because it depends onActionContext

简单解释一下，就是说

execAndWait 会导致执行的Action 在另外一个线程中被执行，而getText 依赖 ActionContext ，他从 ActionContext 中获得当前的Locale 从而根据语言的不同加载不同的文字，可是，由于ActionContext 是ThreadLocal 的，而execAndWait 新开线程的时候并没有把父线程的ActionContext 传递给子线程结果导致在新开的子线程中的ActionContext中的数据都是null ,因此出现异常信息就不足为怪了。

解决方法为

To fix this, you need to copy the parent threads ActionContext into the execAndWait thread. You can do this by extending the BackgroundProcess class, implementing the beforeInvocation()and afterInvocation() methods, and extending ExecuteAndWaitInterceptor, implementing the getNewBackgroundProcess() method.

代码例子如下,注意，原文中作者的代码存在多线程同步问题，具体体现在

beforeInvocation

1	beforeInvocation

被调用的时候，得到的 context 为null ,导致注入失败。

因此需要重载两个类，来解决这个问题

import org.apache.struts2.interceptor.BackgroundProcess;
import org.apache.struts2.interceptor.ExecuteAndWaitInterceptor;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;

public class ExecAndWaitInterceptorEx extends ExecuteAndWaitInterceptor {

	private static final long serialVersionUID = -4456744368791451159L;
	  /**
     * {@inheritDoc}
     */
    @Override
    protected BackgroundProcess getNewBackgroundProcess(String arg0, ActionInvocation arg1, int arg2) {
    	ActionInvocationEx aActionInvocationEx = new ActionInvocationEx(arg1,ActionContext.getContext());
        return new BackgroundProcessEx(arg0, aActionInvocationEx, arg2);
    }

    private class BackgroundProcessEx extends BackgroundProcess {
		public BackgroundProcessEx(String threadName,
				ActionInvocation invocation, int threadPriority) {
			super(threadName, invocation, threadPriority);
		}

		private static final long serialVersionUID = -9069896828432838638L;
        /**
         * {@inheritDoc}
         * @throws InterruptedException 
         */
        @Override
        protected void beforeInvocation() throws InterruptedException {
        	ActionInvocationEx aActionInvocationEx = (ActionInvocationEx)this.invocation;
        	ActionContext context = aActionInvocationEx.getContext();
            ActionContext.setContext(context);
        }

        /**
         * {@inheritDoc}
         */
       @Override
        protected void afterInvocation() {
            ActionContext.setContext(null);
        }

    }
}

import org.apache.struts2.interceptor.BackgroundProcess;

import org.apache.struts2.interceptor.ExecuteAndWaitInterceptor;

import com.opensymphony.xwork2.ActionContext;

import com.opensymphony.xwork2.ActionInvocation;

public class ExecAndWaitInterceptorEx extends ExecuteAndWaitInterceptor {

private static final long serialVersionUID = -4456744368791451159L;

/**

* {@inheritDoc}

@Override

protected BackgroundProcess getNewBackgroundProcess(String arg0, ActionInvocation arg1, int arg2) {

ActionInvocationEx aActionInvocationEx = new ActionInvocationEx(arg1,ActionContext.getContext());

return new BackgroundProcessEx(arg0, aActionInvocationEx, arg2);

}

private class BackgroundProcessEx extends BackgroundProcess {

public BackgroundProcessEx(String threadName,

ActionInvocation invocation, int threadPriority) {

super(threadName, invocation, threadPriority);

}

private static final long serialVersionUID = -9069896828432838638L;

/**

* {@inheritDoc}

* @throws InterruptedException

@Override

protected void beforeInvocation() throws InterruptedException {

ActionInvocationEx aActionInvocationEx = (ActionInvocationEx)this.invocation;

ActionContext context = aActionInvocationEx.getContext();

ActionContext.setContext(context);

}

/**

* {@inheritDoc}

@Override

protected void afterInvocation() {

ActionContext.setContext(null);

}

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionEventListener;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.ActionProxy;
import com.opensymphony.xwork2.Result;
import com.opensymphony.xwork2.interceptor.PreResultListener;
import com.opensymphony.xwork2.util.ValueStack;

public class ActionInvocationEx implements ActionInvocation {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	private final ActionInvocation mActionInvocation;

	private final ActionContext context;

	public ActionInvocationEx(ActionInvocation aActionInvocation,ActionContext aContext)
	{
		mActionInvocation = aActionInvocation;
		context = aContext;
	}

	public Object getAction() {
		return mActionInvocation.getAction();
	}

	public boolean isExecuted() {
		return mActionInvocation.isExecuted();
	}

	public ActionContext getInvocationContext() {
		return mActionInvocation.getInvocationContext();
	}

	public ActionProxy getProxy() {
		return mActionInvocation.getProxy();
	}

	public Result getResult() throws Exception {
		return mActionInvocation.getResult();
	}

	public String getResultCode() {
		return mActionInvocation.getResultCode();
	}

	public void setResultCode(String resultCode) {
		mActionInvocation.setResultCode(resultCode);
	}

	public ValueStack getStack() {
		return mActionInvocation.getStack();
	}

	public void addPreResultListener(PreResultListener listener) {
		mActionInvocation.addPreResultListener(listener);
	}

	public String invoke() throws Exception {
		return mActionInvocation.invoke();
	}

	public String invokeActionOnly() throws Exception {
		return mActionInvocation.invokeActionOnly();
	}

	public void setActionEventListener(ActionEventListener listener) {
		mActionInvocation.setActionEventListener(listener);
	}

	public void init(ActionProxy proxy) {
		mActionInvocation.init(proxy);
	}

	public ActionInvocation serialize() {
		return mActionInvocation.serialize();
	}

	public ActionInvocation deserialize(ActionContext actionContext) {
		return mActionInvocation.deserialize(actionContext);
	}

	/**
	 * @return the context
	 */
	public ActionContext getContext() {
		return context;
	}
}

import com.opensymphony.xwork2.ActionContext;

import com.opensymphony.xwork2.ActionEventListener;

import com.opensymphony.xwork2.ActionInvocation;

import com.opensymphony.xwork2.ActionProxy;

import com.opensymphony.xwork2.Result;

import com.opensymphony.xwork2.interceptor.PreResultListener;

import com.opensymphony.xwork2.util.ValueStack;

public class ActionInvocationEx implements ActionInvocation {

/**

private static final long serialVersionUID = 1L;

private final ActionInvocation mActionInvocation;

private final ActionContext context;

public ActionInvocationEx(ActionInvocation aActionInvocation,ActionContext aContext)

{

mActionInvocation = aActionInvocation;

context = aContext;

}

public Object getAction() {

return mActionInvocation.getAction();

}

public boolean isExecuted() {

return mActionInvocation.isExecuted();

}

public ActionContext getInvocationContext() {

return mActionInvocation.getInvocationContext();

}

public ActionProxy getProxy() {

return mActionInvocation.getProxy();

}

public Result getResult() throws Exception {

return mActionInvocation.getResult();

}

public String getResultCode() {

return mActionInvocation.getResultCode();

}

public void setResultCode(String resultCode) {

mActionInvocation.setResultCode(resultCode);

}

public ValueStack getStack() {

return mActionInvocation.getStack();

}

public void addPreResultListener(PreResultListener listener) {

mActionInvocation.addPreResultListener(listener);

}

public String invoke() throws Exception {

return mActionInvocation.invoke();

}

public String invokeActionOnly() throws Exception {

return mActionInvocation.invokeActionOnly();

}

public void setActionEventListener(ActionEventListener listener) {

mActionInvocation.setActionEventListener(listener);

}

public void init(ActionProxy proxy) {

mActionInvocation.init(proxy);

}

public ActionInvocation serialize() {

return mActionInvocation.serialize();

}

public ActionInvocation deserialize(ActionContext actionContext) {

return mActionInvocation.deserialize(actionContext);

}

/**

* @return the context

public ActionContext getContext() {

return context;

}

写完之后，在struts.xml 中配置一下拦截器，覆盖掉默认的拦截器，下面是我的配置例子

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
	<constant name="struts.i18n.encoding" value="utf-8"></constant>
	<constant name="struts.multipart.maxSize" value="20971520"/>
    <constant name="struts.devMode" value="true" />

	<package name="FaeSupport" namespace="/" extends="struts-default">
	    <!-- 安装自定义的 execAndWait 拦截器，覆盖掉系统默认的，目的是解决在 execAndWait 出现的时候，Action调用 getText 报java.lang.NullPointerException-->
	    <interceptors > 
            <interceptor name="execAndWait" class="com.FaeSupport.Interceptor.ExecAndWaitInterceptorEx"/> 
        </interceptors > 
		<action name="faesupport" class="com.FaeSupport.Action.FaeSelAction" method="SelParametersCheck">
        <interceptor-ref name="defaultStack"/>
        <interceptor-ref name="execAndWait">
            <param name="delay">1500</param>
        </interceptor-ref>
        <result name="wait">/build_wait.jsp</result>			
		<result name="success">/build_wait.jsp</result>
		</action>
	</package>

</struts>

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE struts PUBLIC

"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"

"http://struts.apache.org/dtds/struts-2.0.dtd">

</interceptors >

<interceptor-ref name="defaultStack"/>

<interceptor-ref name="execAndWait">

</interceptor-ref>

<result name="wait">/build_wait.jsp</result>

<result name="success">/build_wait.jsp</result>

</action>

</package>

</struts>

为Struts 2应用程序创建进度条（等待页面）

Struts 2模拟进度条的原理

对于一些需要较长时间才能完成的任务，在Web开发中，会由HTTP协议会因为超时而断开而面临许多风险，这是在桌面开发不曾遇到的。Struts 2提供的execAndWait拦截器就是为了处理和应付这种情况而设计的。注意，该拦截器不在"defaultStack"中,所以必须在使用它的动作里声明它，并且必须放在拦截器栈的最后一个。

使用了该拦截器后，动作依然正常执行，只是该拦截器会分配一个后台线程处理动作的运行，并在动作完成之前把用户带到一个"等待"页面。，该页面每隔一段时间刷新一次，直到那个后台线程执行完毕为止。如果用户随后又触发了同一个动作，但顶一个动作尚未执行完毕，这个拦截器将继续向用户发送"等待"结果；如果他已经执行完毕，用户会看到该动作的最终结果。
"等待"结果的行为与"dispatcher"结果的行为很相似，但是要注意的是，"等待"结果对应的视图带有如下的meta标签：

<meta http-equiv="refresh" content="5;url=/Struts2/default_progressbar.action"/>

1	<meta http-equiv="refresh" content="5;url=/Struts2/default_progressbar.action"/>

该标签的作用就每隔多少秒就重新加载一次同样的URL。"5"是5秒，"url=/Struts2/default_progressbar.action"表示要加载的URL。
Struts 2是一个灵活强大的框架，如果你不喜欢Struts 2提供的默认"等待页面"，你也可以自己设计自己的等待页面，若在动作声明中，没有找到"等待"结果，将使用默认值。

execAndWait拦截器

execAndWait拦截器可以接收以下参数：

threadPriority：分配给相关线程的优先级，默认值为Thread.NORM_PRIORITY。
delay：向用户发送"等待"结果前的毫秒数，默认值为0。如果你不想立刻发送"等待"结果，可以将该参数设置为一个值。例如，你想让动作超过2秒还未完成时才发送"等待"结果，需要将其值设置为2000.
delaySleepInterval：每隔多少毫秒唤醒主线程（处理动作的后台线程）去检查后台线程是否已经处理完成，默认值是100。这个值设为0时无效。

示例：使用默认视图与自定义视图

创建一个动作类，该动作类的工作为挂起30秒：

public class ProgressbarAction extends ActionSupport
{
    private static final long serialVersionUID = 7441785390598480063L;
    private int  complete = 0;

    // 获取进度值
    public int getComplete()
    {
        complete += 10;
        return complete;
    }

    @Override
    public String execute()
    {
        try
        {
            Thread.sleep(30000);
        }
        catch (InterruptedException e)
        {
            e.printStackTrace();
        }
        return SUCCESS;
    }
}

public class ProgressbarAction extends ActionSupport

{

private static final long serialVersionUID = 7441785390598480063L;

private int complete = 0;

// 获取进度值

public int getComplete()

{

complete += 10;

return complete;

}

@Override

public String execute()

{

try

{

Thread.sleep(30000);

}

catch (InterruptedException e)

{

e.printStackTrace();

}

return SUCCESS;

}

配置struts.xml文件：

<package name="progressbar" extends="struts-default">
    <action name="default_progressbar" class="struts2.suxiaolei.progressbar.action.ProgressbarAction">
        <interceptor-ref name="defaultStack"></interceptor-ref>
        <interceptor-ref name="execAndWait">
            <param name="delay">1500</param>
        </interceptor-ref>
        <result name="success">/state_ok.jsp</result>
    </action>

    <action name="customer_progressbar" class="struts2.suxiaolei.progressbar.action.ProgressbarAction">
        <interceptor-ref name="defaultStack"></interceptor-ref>
        <interceptor-ref name="execAndWait">
            <param name="delay">1500</param>
        </interceptor-ref>
        <result name="wait">/customer_wait.jsp</result>
        <result name="success">/state_ok.jsp</result>
    </action>
</package>

<interceptor-ref name="defaultStack"></interceptor-ref>

<interceptor-ref name="execAndWait">

</interceptor-ref>

<result name="success">/state_ok.jsp</result>

</action>

<interceptor-ref name="defaultStack"></interceptor-ref>

<interceptor-ref name="execAndWait">

</interceptor-ref>

<result name="wait">/customer_wait.jsp</result>

<result name="success">/state_ok.jsp</result>

</action>

</package>

测试页面：

<body>
    <s:a href="/Struts2/default_progressbar.action">default_view</s:a>
    <br />
    <s:a href="/Struts2/customer_progressbar.action">customer_view</s:a>
</body>

<body>

<s:a href="/Struts2/default_progressbar.action">default_view</s:a>

<br />

<s:a href="/Struts2/customer_progressbar.action">customer_view</s:a>

</body>

自定义等待页面：

<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'customer_wait.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">

    <!-- 下面的meta元素才是重点，其他的没什么影响，是IDE自带的  -->
    <meta http-equiv="refresh" content="3;url=/Struts2/customer_progressbar.action">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>

  <body>
    <div>
        Please wait...(<s:property value="complete"/>)% complete
    </div>
  </body>
</html>

<html>

<head>

<title>My JSP 'customer_wait.jsp' starting page</title>

<!--

-->

</head>

<body>

<div>

Please wait...(<s:property value="complete"/>)% complete

</div>

</body>

</html>

最终结果页面：

<body>
    OK!
</body>

<body>

OK!

</body>

在浏览器中输入：http://localhost:8081/Struts2/test.jsp，获得如下页面

首先点击，"default_view"链接：

查看它的源代码：

<html>
    <head>
        <meta http-equiv="refresh" content="5;url=/Struts2/default_progressbar.action"/>
    </head>
    <body>
        Please wait while we process your request...
        <p/>

        This page will reload automatically and display your request when it is completed.
    </body>
</html>