豆子有什么意义？ [英] What's the point of beans?
问题描述
我正在做一些JSP教程，我不明白bean类的意义。它只是获取和设置方法。我们为什么要使用它们？
I've bean doing some JSP tutorials and I don't understand what the point of a bean class is. All it is, is get and set methods. why do we use them?
public class UserData {
String username;
String email;
int age;
public void setUsername( String value )
{
username = value;
}
public void setEmail( String value )
{
email = value;
}
public void setAge( int value )
{
age = value;
}
public String getUsername() { return username; }
public String getEmail() { return email; }
public int getAge() { return age; }
}
和jsp是
<jsp:useBean id="user" class="user.UserData" scope="session"/>
<HTML>
<BODY>
You entered<BR>
Name: <%= user.getUsername() %><BR>
Email: <%= user.getEmail() %><BR>
Age: <%= user.getAge() %><BR>
</BODY>
</HTML>
推荐答案
-
A Bean获得了Java一次编写，随处运行范例的所有好处。
可以控制暴露给应用程序
构建器工具的Bean的属性，事件和方法。
A Bean obtains all the benefits of Java's "write-once, run-anywhere" paradigm. The properties, events, and methods of a Bean that are exposed to an application builder tool can be controlled.
Bean可能被设计为在不同的语言环境中正常运行，这使得它在全球市场中有用。
A Bean may be designed to operate correctly in different locales, which makes it useful in global markets.
可以提供辅助软件来帮助人配置Bean。只有在设置该组件的设计时参数时，才需要此软件
。
不需要包含在运行时环境中。
Bean的配置设置可以保存在持久存储中，并在以后恢复
。
Auxiliary software can be provided to help a person configure a Bean. This software is only needed when the design-time parameters for that component are being set. It does not need to be included in the run-time environment. The configuration settings of a Bean can be saved in persistent storage and restored at a later time.
Bean可以注册以接收来自其他对象的事件，并可以生成将
发送给其他对象的事件。
A Bean may register to receive events from other objects and can generate events that are sent to other objects.
使用 scriptlet （那些< %%> 的东西）确实非常气馁，因为taglibs诞生了（比如 JSTL ）和EL（表达式语言，那些 $ {} 的东西）十多年前。 scriptlet 的主要缺点是：
The use of scriptlets (those <% %> things) is indeed highly discouraged since the birth of taglibs (like JSTL) and EL (Expression Language, those ${} things) over a decade ago. The major disadvantages of scriptlets are:
-
可重用性：您无法重用scriptlet。
Reusability: you can't reuse scriptlets.
可替换性：您不能将scriptlet抽象化。
Replaceability: you can't make scriptlets abstract.
OO-ability：你不能使用继承/组合。
OO-ability: you can't make use of inheritance/composition.
可调试性：如果scriptlet中途抛出异常，你得到的只是一个空白页面。
Debuggability: if scriptlet throws an exception halfway, all you get is a blank page.
可测试性：scriptlet不是单元可测试的。
Testability: scriptlets are not unit-testable.
可维护性：每个saldo需要更多时间来维护混杂/混乱/重复的代码逻辑。
Maintainability: per saldo more time is needed to maintain mingled/cluttered/duplicated code logic.
这篇关于豆子有什么意义？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
