Recent Notes
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Created by Fang on August 03, 2010 19:50:51
Last update: August 03, 2010 19:50:51
The tags <fmt:message> Writes out a formatted message for the current locale and resource bundle, or stores the resulting message to a scoped variable (when the var attribute is specified). Syntax:
<fmt:message key="messageKey" [bundle="resourc... Or, with parameters in body: <fmt:message key="messageKey" [bundle="resourc... <fmt:bundle> Creates a resource bundle for the contained body. Syntax: <fmt:bundle basename="basename" [prefix="prefi... <fmt:setBundle> Sets a resource bundle in a scoped variable, which may be used later by <fmt:message> . Syntax: <fmt:setBundle basename="basename" [var="varNa... <fmt:param> This is used inside a <fmt:message> tag to specify a replacement parameter. <fmt:param value="theParameterValue"/> or <fmt:param>The Parameter Value</fmt:param> Test it Make these additions to the expanded test application : Create 3 resource bundles and place them under src\main\resources . messages_en.properties : label.login=Login label.username=User Name ... messages_es.properties :...
Created by Dr. Xi on July 19, 2010 21:58:34
Last update: July 23, 2010 21:37:23
Parsing XML in Java is really simple:
import java.io.*; import javax.xml.parsers.Docu... The parser implementation details are hidden behind the JAXP API. In case you want to know which parser implementation is used, this is what the JavaDoc for DocumentBuilderFactory.newInstance says: Use the javax.xml.parsers.DocumentBuilderFactory system property. Use the properties file " lib/jaxp.properties " in the JRE directory. This configuration file is in standard java.util.Properties format and contains the fully qualified name of the implementation class with the key being the system property defined above. The jaxp.properties file is read only once by the JAXP implementation and it's values are then cached for future use. If the file does not exist when the first attempt is made to read from it, no further attempts are made to...
Created by Fang on April 02, 2010 21:45:47
Last update: July 17, 2010 02:55:06
This is built upon the simple test application for JSTL , which contained a single servlet and a single JSP page. If I want to use it to test all available JSTL tags, the servlet and JSP page would be too complicated. Instead, I want to group the JSTL tags into separate JSP pages and display each group based on the requested URL. For example, if the URL ends with /CoreBasic , I'll display a page that contains the basic core tags; if the URL ends with /I18N , I'll display a page that contains the internationalization tags (e.g., <fmt:message> ). Furthermore, I want to delegate the handling of each group of tags to separate Java classes. This is the application I'll use for the...
Created by James on June 30, 2010 19:04:45
Last update: July 03, 2010 21:24:33
Technically, file upload cannot be handled by Ajax, because XMLHttpRequest (XHR) does not handle file inputs. All techniques not using Flash rely on an invisible iframe as the upload form submit target. JavaScript then grabs the response content from the iframe and present it, giving the same illusion as Ajax. webtoolkit AIM The technique by webtoolkit is very simple. It involves 3 simple steps: include the AIM script, implement the start/finish JavaScript functions, and add an onsubmit handler to the normal file upload form. The hooked up form looks like:
<head> <script type="text/javascript" src="webt... The AIM script is also quite simple: /** * * AJAX IFRAME METHOD (AIM) * http... The above code only supports HTML responses. In order to support JSON responses, the above...
Created by magnum on July 01, 2010 15:38:49
Last update: July 01, 2010 15:39:53
From Apache HTTPD docs: When acting in a reverse-proxy mode (using the ProxyPass directive, for example), mod_proxy_http adds several request headers in order to pass information to the origin server. These headers are: X-Forwarded-For The IP address of the client. X-Forwarded-Host The original host requested by the client in the Host HTTP request header. X-Forwarded-Server The hostname of the proxy server. Be careful when using these headers on the origin server, since they will contain more than one (comma-separated) value if the original request already contained one of these headers. For example, you can use %{X-Forwarded-For}i in the log format string of the origin server to log the original clients IP address, but you may get more than one address if the request passes through...
Created by Dr. Xi on June 11, 2010 23:11:59
Last update: June 11, 2010 23:14:02
Given a simple XML file like this:
<?xml version="1.0"?> <root id="1"> ... Calling Document.getElementById returns null (surprisingly!): import java.io.*; import org.w3c.dom.*; impo... In fact the JavaDoc says something along the lines that getElementById returns the Element that has an ID attribute with the given value. An attribute with the name "ID" or "id" is not of type ID unless it is so defined. How is an attribute defined as an ID attribute ? With a DTD or schema. If you are not validating the XML, then the API is useless. So, what to do if you want to find an element for which the attribute named "id" has a given value? Several options were offered in GetElementById Pitfalls . One of them is to...
Created by Fang on April 01, 2010 22:24:58
Last update: April 02, 2010 02:49:38
In this note I'll show you how to create and package a JSP custom tag. The purpose of this tag is to display a random splash image for a home page, among a set of images. We should be able to add or delete candidate splash images from the WAR archive without the need to change the JSP. This is the intended use of the tag:
<%@ taglib uri="http://custom.tag.com/demo" prefix... In the above example you provide a set of images named splash*.png (e.g., splash1.png, spalsh2.png, ...), and the tag will pick a random one to display when the JSP is rendered. Let's get started. I'll use Maven for this purpose. Create the standard Maven directory structure ./pom.xml ./src ./src/main ./src/main/jav... pom.xml <project xmlns="http://maven.apache.org/POM/4.0.0"... SplashTag.java package tagdemo; import java.util.ArrayList......
Created by Fang on March 23, 2010 02:33:54
Last update: March 31, 2010 04:16:40
Expression Language (EL) was introduced since JSTL 1.0, it is part of the JSP spec since JSP 2.0/JSTL 1.1. There's no JSTL without EL. But don't let the name scare you, EL is not another programming language. It's just a simple construct: ${expr} , which means that instead of taking expr literally, it should be evaluated in the page using any page/request/session/application variables exposed to that page. For example, if you put
Hello ${world}! in your JSP, world will be evaluated in the page context. If you had set a value for world before, for example, request.setAttribute("world", "John Doe"); in your Struts action class or a servlet, the JSP page would show: Hello John Doe! There were confusions about EL support in various servlet/JSP/JSTL version...
Created by nogeek on March 21, 2010 20:30:53
Last update: March 21, 2010 20:37:53
Port 8080 is undoubtedly overused. You may want to change JBOSS to a port other than the default 8080.
Edit the file $JBOSS_HOME/server/default/conf/bindingservice.beans/META-INF/bindings-jboss-beans.xml and change the webserver port from 8080 to 8088:
<bean class="org.jboss.services.bi...
The XSLT at the bottom of the file transforms port 8080 in $JBOSS_HOME/server/default/deploy/jbossweb.sar/server.xml to 8088 specified in this file.
Created by Dr. Xi on February 12, 2010 22:39:15
Last update: February 12, 2010 22:39:15
When you start Tomcat for the first time, you may get the "port 8080 is already in use" error. Indeed, port 8080 is commonly used by a lot of development servers by default (Oracle XE for another example). Luckily, it's quite easy to ask Tomcat to use a different port. I use port 8086, which is a natural next step and superior to 8080.
Simply edit $CATALINA_BASE/conf/server.xml and change 8080 to 8086:
<!-- A "Connector" represents an endpoint by w...
If you have not configured Tomcat 6 for multiple instances by setting a CATALINA_BASE directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME , the directory into which you have installed Tomcat 6.
