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JSP custom tags example with body

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>
 ...

Some notes on writing to a file owned by an app in SD card on Android

Created by lokf on January 13, 2012 14:10:42 Last update: January 13, 2012 14:10:42

For some reason I don't know writing to files in Android is very complicated and tedious. Here is some code for those who might need it. Apps should write in the SD in the directory /Android/data/package_name/files/ so that it is deleted with the app uninstall. package randomname; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.FileWriter; import java.io.IOException; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.nio.ByteBuffer; import android.content.Context; import android.os.Environment; import android.util.Log; public class FileIOLibrary { String packageName; boolean mExternalStorageAvailable = false; boolean mExternalStorageWriteable = false; FileIOLibrary(String packageNamep) { this.packageName=packageNamep; } public boolean isExternalStorageAvailable() { updateExternalStorageState(); return mExternalStorageAvailable; } public boolean isExternalStorageWritable() { updateExternalStorageState(); return mExternalStorageWriteable; } /** * writes the current state of SD card to the corresponding variables */ void updateExternalStorageState() {...

Embed JavaScript in JSF Facelets

Created by Fang on November 28, 2011 21:04:15 Last update: November 28, 2011 21:04:15

Some innocent looking JavaScript may cause a fatal error in a Facelet page. For example:

<script type="text/javascript">
 
 if (items.lengt...

<script type="text/javascript">
 
 // jQuery code ...

Because Facelet is strict XML, therefore, < and > must be escaped. There are several ways to deal with this: Do not embed JS code directly in the page. Put the code in .js files and include it in the page with the src attribute. Put JS code in a CDATA section:

<h:outputScript target="head">
 
         <![CDATA...

Use XML entities:

<script type="text/javascript">
 
 // jQuery code ...

Android write to file (internal storage)

Created by freyo on April 15, 2011 09:00:54 Last update: April 15, 2011 09:00:54

Sample code for writing to a file in the internal storage. There are three steps: Open the file with Context.openFileOutput , which returns java.io.FileOutputStream . Write to the file. Close the file.

import java.io.*;
 
 import android.content.Contex...

The second parameter to openFileOutput is the operating mode. Available values are: Context.MODE_PRIVATE Context.MODE_APPEND Context.MODE_WORLD_READABLE Context.MODE_WORLD_WRITEABLE The file is saved in /data/data/<package_name>/files .

Java read file as byte array

Created by alfa on April 06, 2011 12:48:44 Last update: April 06, 2011 12:48:44

package com.demo.io;
 
 
 
 import java.io.*;
 
 
...

Find where a Java class comes from, recursively

Created by Dr. Xi on January 14, 2010 00:28:27 Last update: March 30, 2011 15:37:44

A task that a Java developer does so frequently is to find out where a certain class can be found - to resolve compilation errors, classpath issues, or version conflicts of the same class introduced by multiple class loaders. A long while back I wrote a simple Perl script to perform the task. Later I was informed that there are Swing based Jar Browser and Jars Browser . Then, there are a couple of shell one-liners: # one liner 1 find -name "*.jar" -print0 | xarg... But all of them share the same problem: if a class is in a jar nested in another jar, it cannot be found. Such is the case for a class inside a jar under the WEB-INF/lib directory of a...

Java PrintWriter character encoding example

Created by Dr. Xi on March 02, 2011 11:39:18 Last update: March 09, 2011 12:19:30

Some peculiarities about Java PrintWriter: PrintWriter never throws any exceptions. From JavaDoc : Methods in this class never throw I/O exceptions, although some of its constructors may. The client may inquire as to whether any errors have occurred by invoking checkError(). When error occurs, you'll never know anything more than that it occured, because checkError returns boolean. When a character is out of the range of the character encoding of the PrintWriter, it prints a question mark (?). But this is not an error. Test code: import java.io.*; public class TestPrintWri... Latin1 test result: java TestPrintWriter iso-8859-1 | od -bc 000000... UTF-8 test result: java TestPrintWriter utf-8 | od -bc 0000000 141... Also, the constructor throws a FileNotFoundException when you try to write to a...

python zip file example

Created by mak on March 04, 2011 14:17:32 Last update: March 04, 2011 14:18:35

To create a zipfile in python: Code:

#!/usr/local/bin/python
 
 import zipfile
 
 
 
 #...

Test

unzip -l test.zip
 
 Archive:  test.zip
 
   Lengt...

To read a zipfile in python: Code:

#!/usr/local/bin/python
 
 import zipfile
 
 
 
 #...

JavaScript array map function

Created by Dr. Xi on October 07, 2010 19:20:55 Last update: January 11, 2011 19:59:17

Like the string trim function, Firefox provides a native implementation for array map, IE doesn't. So we have to create our own map function for Array :

if(typeof Array.prototype.map !== 'function') {
 
...

Test page:

<html>
 
     <head>
 
         <title>Array Map</...

PostgreSQL JDBC Blob weirdness

Created by voodoo on November 01, 2010 22:26:00 Last update: November 01, 2010 22:26:00

Some weirdness observed while updating BLOB with PostgreSQL JDBC driver: LOB position offset starts at 1 (not 0 as in IO input stream). When you call setBinaryStream(long pos) , pos must be greater than 0. I think this is JDBC standard behavior. When you write to a BLOB output stream, new contents overwrite existing contents. Old contents are not automatically truncated. If new content length is shorter than old contents, the old contents will remain after the position where new content ended. You can call Blob.truncate(long len) to truncate existing contents. However , there seems to be an discrepancy between the JDBC doc and PostgreSQL JDBC driver. The JDBC JavaDoc states that: Truncates the BLOB value that this Blob object represents to be len bytes...

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