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Created by magnum on July 26, 2010 15:55:41
Last update: March 28, 2012 15:28:02
Given the URL:
http://www.mydomain.com/myWebApp/theServlet/p1/p2/p3;sid=123?param=abc
This would be the output of the various method calls on HttpServletRequest :
String scheme = request.getScheme(); // ...
Created by Fang on January 28, 2012 13:24:09
Last update: January 28, 2012 13:31:22
This is a simple JSP custom tags library with tag body. Just like the JSF counterpart , it splits a string and repeats the body for each word, i.e., with this markup:
<%@ taglib uri="http://custom.tag.com/demo" prefix...
output:
<html>
<body>
<p>Hello Tigger!</p>
<p>H...
With Maven, this is the directory structure:
./src
./src/main
./src/main/resources
./s...
There are three files to write:
pom.xml :
<project xmlns="http://maven.apache.org/POM/4.0.0"...
src/main/java/tagdemo/IterateTag.java :
package tagdemo;
import java.io.IOException...
src/main/resources/META-INF/demotag.tld :
<?xml version="1.0" encoding="UTF-8"?>
<!DO...
Build with:
mvn clean install
To use it as a dependency in other Maven projects:
<dependency>
<groupId>tag-demo</groupId>
...
Created by Fang on November 08, 2011 20:55:00
Last update: November 21, 2011 18:19:44
In the simple taglib example , I used a tag handler class to implement a taglib. This is an example to implement a taglib with a UI component. The purpose is to use a custom tag to split a string and print each part in a separate paragraph, i.e., print
<p>john</p> <p>steve</p> <p>mike</p> with custom tag <my:foreach> : <my:foreach var="who" value="john steve mike"> ... These are the files: pom.xml <project xmlns="http://maven.apache.org/POM/4.0.0"... src/main/java/com/example/UIForeash.java : package com.example; import java.io.IOExcep... src/main/resources/META-INF/faces-config.xml : <?xml version="1.0" encoding="UTF-8"?> <faces-c... src/main/resources/META-INF/foreach.taglib.xml : <?xml version="1.0" encoding="UTF-8"?> <facelet... How to use: Put the JAR file generated by the above project in the WEB-INF/lib folder of the web app. If the web app is a Maven project, just add the taglib project as a dependency:...
Created by magnum on September 27, 2011 21:51:05
Last update: September 28, 2011 18:02:49
Client socket usually does not call bind . But I've seen code that does and it was puzzling to me what bind does to a client socket. Therefore, this little test program. It retrieves a web url and displays info about the socket. You can optionally give a bind host name/ip and port and see what it does.
Here are my test results:
$ ./client www.google.com
Local addr: 172.16.0....
This is the code:
#include <stdio.h>
#include <stdlib.h>
#incl...
Created by Dr. Xi on March 24, 2011 12:11:14
Last update: March 24, 2011 12:22:03
This is the task: your client wants to know how the web application is used. That is pretty easy. A plethora of commercial tools or any of the free log analysis tools such as analog and AWStats would fit the bill. But here's the catch: they want to know not only what pages are visited by how many people and when, but also who logged in and did what. Your application is using form based authentication and therefore, everyone is anonymous in the web access log. What to do? This is a servlet filter that generates a web access log with authenticated user info that can be fed to log analysis tools such as analog and AWStats . Filter code (the output format is Apache...
Created by Dr. Xi on November 23, 2010 20:20:01
Last update: March 01, 2011 13:38:51
I tried to find a GZIP compression servlet filter to compress a large log file that we send down to the browser. Most of the implementations I found were overly complicated and many buggy. This is a simple implementation that worked for me. The filter:
package filter.demo; import java.io.*; i... Config web.xml : <filter> <filter-name>gzipFilter</filte... The ugly anonymous inner class could have been avoided if the servlet API did not insist on ServletResponse.getOutputStream returning the bogus ServletOutputStream class (instead of the plain OutputStream ). Additional Note: In an earlier version of this filter, the gzip headers were added in doFilter , like this: // This is NOT good! if (supportsGzip) { ... It turned out that the ServletResponse methods sendError bypasses the gzip...
Created by Fang on August 10, 2010 21:37:36
Last update: October 25, 2010 20:18:47
The tags <fmt:formatNumber> Format a numeric value as number , currency or percentage - controlled by the type attribute (defaults to number if type is missing). Syntax:
<fmt:formatNumber value="numericValue" [type="... Attributes: Name Dynamic? Type Description value true String or Number Numeric value to be formatted. type true String Specifies whether the value is to be formatted as number, currency, or percentage. pattern true String Custom formatting pattern, must follow the pattern syntax specified by the class java.text.DecimalFormat . currencyCode true String ISO 4217 currency code. Applied only when formatting currencies (i.e. if type is equal to "currency"); ignored otherwise. currencySymbol true String Currency symbol. Applied only when formatting currencies (i.e. if type is equal to "currency"); ignored otherwise. It is used only when currencyCode is...
Created by Fang on August 16, 2010 21:44:41
Last update: August 16, 2010 22:01:46
The tags <sql:query> Queries a database. Syntax:
<sql:query sql="sqlQuery" var="varName" [scope... or, put the query within the element body: <sql:query var="varName" [scope="{page|req... Attributes: Name Dynamic? Type Description sql true String SQL query statement. dataSource true javax.sql.DataSource or String Data source associated with the database to query. A String value represents a relative path to a JNDI resource or the JDBC parameters for the DriverManager class. maxRows true int The maximum number of rows to be included in the query result. If not specified, or set to -1, no limit on the maximum number of rows is enforced. startRow true int The returned Result object includes the rows starting at the specified index. The first row of the original query result set is at index...
Created by Fang on April 04, 2010 04:12:14
Last update: July 21, 2010 14:52:58
The tags <c:if> The <c:if> tag may be used with or without body content:
<!-- Without body content, used to export vari... In my opinion, the version without body content is pretty much useless (the <c:set> tag is a lot more meaningful for this purpose). If body content exists, it is inserted into the page if the testCondition is true . Optional attributes var and scope may be specified. If var is specified, a variable whose name is the value of var is exported to the associated scope ( pageScope if no scope is specified). The type of the exported variable is Boolean and its value is the value of the testCondition . <c:choose>, <c:when>, <c:otherwise> These tags imitate the Java control structure if...else...
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...
