执行该方法，如果成功会返回一个对象，否则抛出异常。
The method executes and either an object is returned, if successful, or an exception is thrown.
如果在处理jsp页面时有一个异常抛出的话，exception对象就会立即通过隐式声明的exception变量的方式抛给指定的错误页面。
Whenever an exception is thrown while processing your JSP page, the exception object will immediately be thrown to the designated error page by means of the implicitly declared exception variable.
如果还没有创建XMLHttpRequest对象，或者已经发送了请求，那么checkRequest()函数将抛出一个异常。
The checkRequest() function will throw an exception if the XMLHttpRequest object has not been created or if the request has already been sent.
为了解决这一问题，可以在抛出异常语句期间，在异常对象的构造函数中生成一个堆栈跟踪。
To deal with this, you can generate a stack trace in the constructor of the exception object during the throw exception statement.
该异常的抛出，表明代码企图把对象的类型转换成一个子类，而该对象并不是这个子类的实例。
Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance.
如果文档没有被解析且对象在30秒内进行持久化，则服务器将抛出一个异常且对象将不会创建。
If the document is not parsed and the objects made persistent within 30 seconds, then the server will throw an exception and the objects will not be created.
当抛出一个表达式的时候，被抛出对象的静态编译时类型将决定异常对象的类型。
When an exception is thrown, the static, compile-time type of the thrown object determines the type of the exception object.
做法范围内的对象被破坏时，该方法将抛出一个异常？
Do method-scoped objects get destroyed when the method throws an exception?
当抛出一个异常的时候，通常在抛出点构造将抛出的对象，该对象表示出了什么问题，所以我们知道确切的异常类型。
When we throw an exception, we usually construct the object we are going to throw at the throw point. That object represents what went wrong, so we know the precise exception type.
当抛出一个异常的时候，通常在抛出点构造将抛出的对象，该对象表示出了什么问题，所以我们知道确切的异常类型。
When we throw an exception, we usually construct the object we are going to throw at the throw point. That object represents what went wrong, so we know the precise exception type.
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