Java 异步回调失败

在我的应用程序中，我需要将字符串值添加到文件（.property文件，如果重要的话）。用户在gwt GUI中输入该值。以下是它的重要部分：

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);
    }

所有接口都存在。 当我运行代码并按下gui中的“提交”按钮时，我看到两个asynccallback都失败了（如您所见，Window.alert显示“空指针异常”，尽管我发送给方法的值不是空的）。为什么会这样？你能给我提个建议吗

UPD以下是firebug显示的错误：

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

---

问题解决了：代码中有一个简单的错误。我把括号放错地方了：

//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";
    }

---

我建议您使用 -造型漂亮 然后再次检查firebug输出；与更新的未捕获异常相比，它可能会给您提供更好的线索

---

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。

服务器是否接收到请求？服务器日志呢？事实上，我是个编程新手，不能这么说，因为我不知道怎么做。只有firefox中的firebug显示文章有适当的值和一个错误，我不明白这是什么。我现在就更新我的帖子

//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";
    }