StackOverflowError在Seam / Spring WebFlow中的应用

Question

我们正在逐步用Spring和Spring取代Seam组件。

运行JMeter-几个小时后，日志就会被StackOverFlowErrors弄得乱七八糟：

javax.servlet.ServletException: Servlet execution threw an exception
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:313)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:341)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:530)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
...
Caused by: java.lang.StackOverflowError
    at org.jboss.seam.jsf.SeamApplication.getMessageBundle(SeamApplication.java:264)
    at org.springframework.faces.webflow.FlowApplication.getMessageBundle(FlowApplication.java:214)
    at org.jboss.seam.jsf.SeamApplication.getMessageBundle(SeamApplication.java:264)
    at org.springframework.faces.webflow.FlowApplication.getMessageBundle(FlowApplication.java:214)
    at org.jboss.seam.jsf.SeamApplication.getMessageBundle(SeamApplication.java:264)
    at org.springframework.faces.webflow.FlowApplication.getMessageBundle(FlowApplication.java:214)
    at org.jboss.seam.jsf.SeamApplication.getMessageBundle(SeamApplication.java:264)

因此，getMessageBundle方法由两个实例调用: SeamApplication和FlowApplication。

看看javax.faces.application.Application类，它说：

“因为这个实例是共享的，所以它必须以线程安全的方式实现。”

也许这两个应用程序实例试图访问相同的包，这会导致竞争条件？

编辑:在应用程序不再响应后，我们重新启动服务器，现在错误出现在另一个地方：

Caused by: java.lang.StackOverflowError
at org.jboss.seam.contexts.BasicContext.get(BasicContext.java:49)
at org.jboss.seam.contexts.BasicContext.get(BasicContext.java:44)
at org.jboss.seam.core.Init.instance(Init.java:117)
at org.jboss.seam.jsf.SeamApplication$ConverterLocator.<init>(SeamApplication.java:140)
at org.jboss.seam.jsf.SeamApplication.createConverter(SeamApplication.java:122)
at org.springframework.faces.webflow.FlowApplication.createConverter(FlowApplication.java:161)
at org.jboss.seam.jsf.SeamApplication.createConverter(SeamApplication.java:126)
at org.springframework.faces.webflow.FlowApplication.createConverter(FlowApplication.java:161)
at org.jboss.seam.jsf.SeamApplication.createConverter(SeamApplication.java:126)

最后2行在日志文件中重复数千次。

我们正在使用以下组件-版本：

JSF-1.2

Seam-2.2.0

春季WebFlow 2.3.4

Spring 3.0.5

更新任何组件都不是一个选项。

Answer 1

SeamApplication和FlowApplication在正确委托包装的应用程序方面都有错误。修复它的一种方法是通过FlowApplicationFactory。

首先获取它的原始源代码并将其放到webapp项目的Java文件夹中，维护它的原始包。你不一定需要操纵罐子。/WEB-INF/classes中的类比JAR中的类具有更高的类加载优先级。

然后按如下方式操作类(基于OmniFaces OmniApplicationFactory)：

public class FlowApplicationFactory extends ApplicationFactory {

    private final ApplicationFactory wrapped;
    private volatile Application application;

    public FlowApplicationFactory(ApplicationFactory wrapped) {
        this.wrapped = wrapped;
    }

    @Override
    public Application getApplication() {
        return (application == null) ? createFlowApplication(wrapped.getApplication()) : application;
    }

    @Override
    public synchronized void setApplication(Application application) {
        wrapped.setApplication(createFlowApplication(application));
    }

    private Application createFlowApplication(final Application application) {
        Application newApplication = application;

        while (!(newApplication instanceof FlowApplication) && newApplication instanceof SeamApplication) {
            newApplication = ((SeamApplication) application).getDelegate();
        }

        if (!(newApplication instanceof FlowApplication)) {
            newApplication =  new FlowApplication(application);
        }

        return (this.application = newApplication);
    }

}

因此，在创建FlowApplication时，它将首先检查包装好的应用程序(如果它之前还没有创建)，如果是的话，则重新使用它。

请注意，SeamApplication依赖是尴尬的，但这只是为了修复它。JSF2通过新的ApplicationWrapper类使它更容易使用，您可以在createFlowApplication()块中使用它而不是SeamApplication。

如果这一切仍然不起作用，那么也许SeamApplicationFactory是在 FlowApplicationFactory之后初始化的。您可以强制排序，方法是按照所需的顺序显式地重新声明webapp自己的faces-config.xml中的faces-config.xml条目( by固定为最后一个)：

<factory>
    <application-factory>org.jboss.seam.jsf.SeamApplicationFactory</application-factory>
    <application-factory>org.springframework.faces.webflow.FlowApplicationFactory</application-factory>
</factory>

否则，您可能希望对SeamApplicationFactory (显然是使用代码中交换的FlowApplication和SeamApplication )执行上述操作。