Java Beans 面试题与答案
问题 36. What are externizable interface?
Use the Externalizable interface when you need complete control over your bean's serialization (for example, when writing and reading a specific file format).
To use the Externalizable interface you need to implement two methods: readExternal and writeExternal. Classes that implement Externalizable must have a no-argument constructor.
问题 37. What are the purpose of introspection?
A growing number of Java object repository sites exist on the Internet in answer to the demand for centralized deployment of applets, classes, and source code in general. Any developer who has spent time hunting through these sites for licensable Java code to incorporate into a program has undoubtedly struggled with issues of how to quickly and cleanly integrate code from one particular source into an application.
The way in which introspection is implemented provides great advantages, including:
► Portability - Everything is done in the Java platform, so you can write components once, reuse them everywhere. There are no extra specification files that need to be maintained independently from your component code. There are no platform-specific issues to contend with. Your component is not tied to one component model or one proprietary platform. You get all the advantages of the evolving Java APIs, while maintaining the portability of your components.
► Reuse - By following the JavaBeans design conventions, implementing the appropriate interfaces, and extending the appropriate classes, you provide yourcomponent with reuse potential that possibly exceeds your expectations.
问题 38. What is property editor in java beans?
A property editor is a tool for customizing a particular property type. Property editors are activated in the Properties window. This window determines a property's type, searches for a relevant property editor, and displays the property's current value in a relevant way.
问题 39. Write a simple bean program?
Write the SimpleBean code. Put it in a file named SimpleBean.java, in the directory of your choice. Here's the code:
import java.awt.Color;
import java.beans.XMLDecoder;
import javax.swing.JLabel;
import java.io.Serializable;
public class SimpleBean extends JLabel
implements Serializable {
public SimpleBean() {
setText( "Hello world!" );
setOpaque( true );
setBackground( Color.RED );
setForeground( Color.YELLOW );
setVerticalAlignment( CENTER );
setHorizontalAlignment( CENTER );
}
}
问题 40. Difference between java bean and bean?
A Java Bean is a software component written in the Java programming language that conforms to the JavaBeans component specification. The JavaBeans APIs became part of the "core" Java APIs as of the 1.1 release of the JDK.
The JavaBeans specification defines a Java-based software component model that adds a number of features to the Java programming language. Some of these features include:
► introspection
► customization
► events
► properties
► persistence
Enterprise JavaBeans (EJBs) are Java-based software components that are built to comply with Java's EJB specification and run inside of an EJB container supplied by a J2EE provider. An EJB container provides distributed application functionality such as transaction support, persistence and lifecycle management for the EJBs.
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- What are Java Beans?
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