javabeans | 易学教程

What is the best way to implement notification about property change?

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问题 A have a bean (POJO-like) and want to make model for GUI component of it. So I need to notify about each property change in order GUI component can reflect. How to do this? Should I put notification and listener storage code just inside my bean? But this will make it "dirty". May be write some wrapper? But this will duplicate getters and setters. Are there any libraries and/or helper objects for this in Commons or somewhere else? UPDATE Also suppose I have AbstractList<E> implementation. How

Set property in Java bean class

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I have created a from which have a text field name 'empId' whose value is set into a bean class through a jsp page using <jsp:setProperty> tag note:empId is of int type in bean class when i write the following code <jsp:setProperty name="mybean" property="empId" value="empId"/> It will work fine but when i write the following code <jsp:setProperty name="mybean" property="empId" value="<%=request.getParameter("empId")%>"/> then it is not working gives the exception JasperException Use EL expression. use ${param.empId} if you want to map request parameter. <jsp:setProperty name="mybean" property

Beans serialization in JSP

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Why some times tutorials make beans implement Serializable object and others do not? I know that object should be serialized when I want to send it through a network, so does that prove that each bean used in sessions should implements Serializable objects and beans defined in JSP pages should not since they are not transferred using HTTP requeset I know that object should be serialized when I want to send it through a network, so does that prove that each bean used in sessions should implements Serializable You seem to believe that objects in a session are sent to the client in the http

Spring bean's DESTROY-METHOD attribute and web-application “prototype”d bean

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问题 Can get work the attribute "destroy-method". First, even if I type non-existing method name into "destroy-method" attribute, Spring initialization completes fine (already strange!). Next, when a bean has a "prototype" scope, then I suppose it must be destroyed before the application is closed. That not happens, it is simply never called in my case. Though, after extracting this bean I can call this method explicitly and it does its job. Could you explain why this method is never called in my

How can share bean from external library to GWT client?

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问题 I have a question about share the java bean in library to gwt client I know bean share between GWT client and server usually put into package domain.shared. However, how can I make use of existing bean from external jar library on GWT client? Because I always got this message. No source code is available for type xxxx.xxxx.bean did you forget to inherit a required module? 回答1: Given that your beans are in the package xxx.xxx.bean , and they are in an imported my_beans.jar library. Create a

jsf/primefaces load indicator during init of the bean

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问题 In my JSF/Primefaces project, I have a lot of data loading in the init (postconstruct) method of my beans. That's why I would like to show an gif indicator during the bean load. I tried with primefaces and the Ajax status (programmatic version of the showcase) http://www.primefaces.org/showcase/ui/ajaxStatusScript.jsf So I added this to the template of my project <p:dialog modal="true" widgetVar="loadWidget" header="Status" draggable="false" closable="false"> <p:graphicImage value="../images

java.lang.InstantiationException: bean [name] not found within scope

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问题 I am learning how to use jsp and beans now, and can't understand what the issue I'm having. I am trying to create a bean like this: ... and am getting the error: java.lang.InstantiationException: bean reservation not found within scope I have looked around online, and most people seem to recommend using class="..." instead of type="...", or using an import statement. I am already doing the former and tried the latter...any ideas? This is the bean: package homework10; public class Reservation

Java beans, annotations: What do they do? How do they help me?

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Here is what what I understand so far: Java beans are just to help other things (visual things?) interact with your code. I think that this is mostly for UI stuff because it is easier to design this visually. Is it bad practice to use Java beans for non-UI things? Java beans have getter and setter methods (bad OOP practice) and are serializable. In terms of annotations, I think that user defined annotations do not provide any functionality. Some annotations like @depretiated raise compiler warnings. Can user defined annotations do this somehow? Are user defined annotations good for anything

How to PROPERLY inject Grails services using Spring resource.groovy

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问题 Using Grails 2.2.1 I have the following Grails services defined: package poc class TestService { def helperService } class HelperService { } I have used the TestService as follow (resources.groovy): test(poc.TestService) { } jmsContainer(org.springframework.jms.listener.DefaultMessageListenerContainer) { connectionFactory = jmsConnectionFactory destinationName = "Test" messageListener = test autoStartup = true } Everything works except for automatic injection of the helperService, as it is

setter for a boolean variable named like isActive

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问题 I have a property called isActive in my pojo class. When I generated the accessors for this property using Eclipse IDE, it generates following getters and setters Getter : isActive() Setter : setActive() However, when I try to write this property using ibatis framework by mentioning property name as "isActive" , it cribs about not able to find any WRITEABLE propery named 'isActive'. The problem I think lies with not able to deduce the correct property name by inferring setter as setIsActive()