Jsf 在MethodExpression.invoke（）上找不到方法异常

我需要以编程方式调用我的一个支持bean中的方法。我已经看了几个例子，从我所能看到的，这个“应该”起作用

我的代码：

UIData data = (UIData)component;
fc = FacesContext.getCurrentInstance();
elc = fc.getELContext();

elFactory = fc.getApplication().getExpressionFactory();
mexp =
    elFactory.createMethodExpression(elc, data.getValueExpression("value").getExpressionString(), Result.class, new Class[]{});
Object methodResult = mexp.invoke(elc, null);

public Result getCustomer() {
    Result result = null;
    try {
        ...perform database call
    } catch (Exception e) {
        log.error(e);
    }
    return result;
}

“data.getValueExpression（“value”）.getExpressionString（）返回字符串：

#{reports.customer}

关于我正在呼叫的bean的信息（不知道这些是否相关）：
类的托管bean名称是“report”
类在会话范围内
类实现可序列化
我正在调用的方法的访问修饰符是
方法签名中没有参数

我试图调用的方法：

UIData data = (UIData)component;
fc = FacesContext.getCurrentInstance();
elc = fc.getELContext();

elFactory = fc.getApplication().getExpressionFactory();
mexp =
    elFactory.createMethodExpression(elc, data.getValueExpression("value").getExpressionString(), Result.class, new Class[]{});
Object methodResult = mexp.invoke(elc, null);

public Result getCustomer() {
    Result result = null;
    try {
        ...perform database call
    } catch (Exception e) {
        log.error(e);
    }
    return result;
}

堆栈跟踪摘录

SEVERE: javax.el.MethodNotFoundException: Method not found: com.npp.beans.reports.SharebackReportsBean@1ebf0d3.customer()
javax.faces.el.EvaluationException: javax.el.MethodNotFoundException: Method not found: com.npp.beans.reports.SharebackReportsBean@1ebf0d3.customer()
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:98)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:98)
    at javax.faces.component.UICommand.broadcast(UICommand.java:311)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:781)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1246)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:77)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:97)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:114)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:308)
...
Caused by: javax.el.MethodNotFoundException: Method not found: com.npp.beans.reports.SharebackReportsBean@1ebf0d3.customer()
    at com.sun.el.util.ReflectionUtil.getMethod(ReflectionUtil.java:155)
    at com.sun.el.parser.AstValue.invoke(AstValue.java:231)
    at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:297)
    at com.npp.business.TableToExcelManager.initExcelWorker(TableToExcelManager.java:247)
    at com.npp.beans.reports.SharebackReportsBean.exportToExcel(SharebackReportsBean.java:439)
    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.sun.el.parser.AstValue.invoke(AstValue.java:234)
    at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:297)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:102)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:84)
    ... 26 more
Mar 23, 2011 11:29:34 AM com.sun.faces.lifecycle.InvokeApplicationPhase execute
WARNING: #{reports.exportToExcel}: javax.el.MethodNotFoundException: Method not found: com.npp.beans.reports.SharebackReportsBean@1ebf0d3.customer()
javax.faces.FacesException: #{reports.exportToExcel}: javax.el.MethodNotFoundException: Method not found: com.npp.beans.reports.SharebackReportsBean@1ebf0d3.customer()
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:114)
    at javax.faces.component.UICommand.broadcast(UICommand.java:311)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:781)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1246)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:77)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:97)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:114)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:308)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

---

非常感谢您的帮助！

您试图将值表达式视为方法表达式。这是行不通的。值表达式指向getter方法（因此可以省略

get

）虽然方法表达式指向操作方法，但可能需要一个额外的参数。由于您已经有了

ValueExpression

，只需直接从中获取值，而不是试图将其视为

MethodExpression

Result result = (Result) data.getValueExpression("value").getValue(elc);

---

您不应该更改视图中的EL字符串。只需将其保持为

value=“#{reports.customer}”

。否则它在正常视图中无法工作。

您试图将值表达式视为方法表达式。这是行不通的。值表达式指向getter方法（因此可以省略

get

）虽然方法表达式指向操作方法，但可能需要一个额外的参数。由于您已经有了

ValueExpression

，只需直接从中获取值，而不是试图将其视为

MethodExpression

Result result = (Result) data.getValueExpression("value").getValue(elc);

您不应该更改视图中的EL字符串。只需将其保留为

value=“#{reports.customer}”

。否则它将无法在正常视图中工作