asynccallback failures

Question

在我的应用程序中，我需要将字符串值添加到文件（.property文件，如果它很重要）。并且用户在gwt GUI中输入这个值。下面是它的重要组成部分：

final Button submit = new Button("Submit"); 
     addButton(submit); 
     submit.addSelectionListener(new SelectionListener<ButtonEvent>() { 
      @Override 
      public void componentSelected(ButtonEvent ce) { 
       keyWord.selectAll(); 
       regexp.selectAll(); 
       if (keyWord.getValue() != null){ 
        setKeyWord(customerId, keyWord.getValue()); 
        keyWord.setValue(""); 
       } 
       if (regexp.getValue() != null){ 
        setRegExp(customerId, regexp.getValue()); 
        regexp.setValue(""); 
       } 

      } 
     }); 
    } 

    private void setKeyWord(final String customerId, final String keyword){ 

     final AsyncCallback<String> callbackItems = new AsyncCallback<String>() { 
      public void onFailure(final Throwable caught) { 
       Window.alert("unable to add " + caught.toString()); 
      } 

      public void onSuccess(final String x) { 
       Window.alert(x); 
      } 
     }; 
     serverManagementSvc.setKeyWords(customerId, keyword, callbackItems); 
    } 

    private void setRegExp(final String customerId, final String regexp){ 

     final AsyncCallback<String> calbackItems = new AsyncCallback<String>() { 
      @Override 
      public void onFailure(Throwable throwable) { 
       Window.alert("unable to add " + throwable.toString()); 
      } 

      @Override 
      public void onSuccess(String s) { 
       Window.alert(s); 
      } 
     }; 
     serverManagementSvc.setRegExp(customerId, regexp, calbackItems); 
    } 

所以我需要使用Asunccallback调用它们是在“服务器的一部分”的方法。 这里是这些方法：

//adds a new keyword to customers properties 
    public String setKeyWords(String customer, String word){ 
     try{ 
       PropertiesConfiguration props = new PropertiesConfiguration("/home/mikhail/bzrrep/DLP/DLPServer/src/main/resources/rules.properties"); 
       String newKeyWord = new String(props.getString("users." + customer + ".keywords" + "," + word)); 
       props.setProperty("users." + customer + ".keywords", newKeyWord); 
       props.save(); 
     }catch (ConfigurationException e){ 
      e.printStackTrace(); 
     } 
     return "keyword " + word + " added"; 
    } 

    // adds a new regexp to customer properties 
    public String setRegExp(String customer, String regexp){ 
     try { 
       PropertiesConfiguration props = new PropertiesConfiguration("/home/mikhail/bzrrep/DLP/DLPServer/src/main/resources/rules.properties"); 
       String newRegValue = new String(props.getString("users." + customer + ".regexps" + "," + regexp)); 
       props.setProperty("users." + customer + ".regexps", newRegValue); 
       props.save(); 
     } catch (ConfigurationException e){ 
      e.printStackTrace(); 
     } 
     return "regexp " + regexp + " added to " + customer + "'s config"; 
    } 

所有接口都存在。 当我运行我的代码并按gui中的“提交”按钮我看到，两个asynccallback失败（Window.alert，如你所见，显示“空指针异常”，尽管我发送给方法的值不为null ）。为什么会这样？你能告诉我什么吗？

UPD这里是错误，是由萤火虫显示：

uncaught exception: java.lang.ClassCastException  
function W8(){try{null.a()}catch(a){return a}} 

Answer 1

解决问题：有在代码的简单错误。我在错误的地方关闭括号：

//adds a new keyword to customers properties 
    public String setKeyWords(String customer, String word){ 
     try{ 
       PropertiesConfiguration props = new PropertiesConfiguration("/home/mikhail/bzrrep/DLP/DLPServer/src/main/resources/rules.properties"); 
       String newKeyWord = new String(props.getString("users." + customer + ".keywords") + "," + word); 
       props.setProperty("users." + customer + ".keywords", newKeyWord); 
       props.save(); 
     }catch (ConfigurationException e){ 
      e.printStackTrace(); 
     } 
     return "keyword " + word + " added"; 
    } 

    // adds a new regexp to customer properties 
    public String setRegExp(String customer, String regexp){ 
     try { 
       PropertiesConfiguration props = new PropertiesConfiguration("/home/mikhail/bzrrep/DLP/DLPServer/src/main/resources/rules.properties"); 
       String newRegValue = new String(props.getString("users." + customer + ".regexps") + "," + regexp); 
       props.setProperty("users." + customer + ".regexps", newRegValue); 
       props.save(); 
     } catch (ConfigurationException e){ 
      e.printStackTrace(); 
     } 
     return "regexp " + regexp + " added to " + customer + "'s config"; 
    } 

Answer 2

我建议你重新编译使用 GWT的代码风格PRETTY ，然后再次检查萤火虫输出;与更新的未捕获异常相比，它可能会给您一个更好的线索。接下来，我建议您在eclipse调试器中运行它，并在客户端和服务器代码中设置断点，然后您可以检查变量并逐步执行代码。