Java setOnAction订阅引发异常的事件 [英] Java setOnAction subscribe to event that throws exception

问题描述

首先请允许我说一下，我不是Java程序员，并且到目前为止还无法理解为什么会这样.

Let me preface this by saying, I am not a Java programmer and have thus far been unable to understand WHY this is the case.

我目前正在从事一项作业，要求我使用JavaFX创建基本的GUI.此GUI的功能要求单击某些按钮才能执行CRUD操作.目前，我已在我的Insert方法中正确设置了所有内容:

I'm currently working on a homework assignment that requires me to create a basic GUI using JavaFX. The functionality of this GUI requires that there are buttons that will perform CRUD operations when clicked. Currently I have everything set up properly in my Insert method:

        public void Insert() throws SQLException{

        //Insert new record here
    }

但是，每当我尝试使用'setOnAction'订阅此方法时，编译器就会告诉我该事件存在未处理的异常:

However, whenever I try to subscribe to this method using 'setOnAction', the compiler is telling me there's an unhandled exception on the event:

btnInsert.setOnAction(e ->Insert());

我想知道是否有一种相对简洁的方式来解决这个问题?到目前为止，我一直无法提出解决方案.

I'm more curious if there's a way to handle this in a relatively succinct way? I've thus far been unable to come up with a solution.

推荐答案

这是因为Java要求您声明所有引发的检查异常-因此，每当调用可能引发检查异常的方法时，都必须捕获该异常或声明你可以自己扔.

That's because Java requires you to declare all checked exceptions you throw - so whenever you call a method that may throw a checked exception, you must either catch it or declare you may throw it yourself.

请参见此问题，以获取有关已检查和未检查的异常的说明(简短版本-未选中继承Error或RuntimeException的任何Exception，而所有其他异常都被选中.)

See this question for an explanation of checked vs. unchecked exception (The short version - any Exception which inherits either Error or RuntimeException is unchecked, while all other exceptions are checked.)

为setOnAction提供lambda时，实际上是在创建

When you are providing setOnAction with a lambda, you are actually creating an anonymous class implementation of EventHandler<ActionEvent>. Since it does not declare it throws any exceptions, neither does your anonymous class (and in fact - it can't).

因此，您有两种解决问题的方法:

So you have two options of solving the problem:

1. 捕获并处理异常:

1. Catch and handle the exception:

btnInsert.setOnAction(e -> {
    try {
        Insert();
    } catch (SQLException ex) {
        // Log error, show error message, etc... Whichever is applicable for your application
    }
});

抛出未检查的异常:

Rethrow an un-checked exception:

btnInsert.setOnAction(e -> {
    try {
        Insert();
    } catch (SQLException ex) {
        throw new RuntimeException(ex); // Or any other subclass of RuntimeException or Error
    }
});

关于在两个选项之间进行选择- Oracle的文档这样说:

As to choosing between the two options - Oracle's documentation says this:

这是最重要的原则:如果可以合理地期望客户端从异常中恢复，请将其设置为已检查的异常.如果客户端无法采取任何措施来从异常中恢复，请将其设置为未经检查的异常.

Here's the bottom line guideline: If a client can reasonably be expected to recover from an exception, make it a checked exception. If a client cannot do anything to recover from the exception, make it an unchecked exception.

当然，所有这些都可以从实际的EventHandler移开，因此可以在没有检查异常的方法上调用它.

Of course, this could all be moved away from the actual EventHandler, so it can be called on a method that is checked-exception-free.

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