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Java utility to convert String (byte array) to hex and reverse

Created by Dr. Xi on June 22, 2011 13:23:19 Last update: April 30, 2012 11:40:06

This is a utility to convert a byte array to hex string, and to convert a hex string back to the original. To convert a String to hex, you must call String.getBytes() first. The utility does not pretend to know your string encoding.

public class StringHexUtil {
 
     public static ...

This also works:

String binaryToHex(byte[] data) {
 
     StringBui...

Export variables with JSP custom tag

Created by Fang on April 16, 2012 13:18:40 Last update: April 16, 2012 13:18:40

Simply call pageContext.setAttribute() to export a variable from within a JSP custom tag:

public class MyCustomVarTag extends TagSupport {
 ...

The availability of the exported variable can be limited in the TLD:

<tag>
 
     <name>setVar</name>
 
     <tag-class...

The availability scopes are: Value Availability NESTED Between the start tag and the end tag. AT_BEGIN From the start tag until the scope of any enclosing tag. If there’s no enclosing tag, then to the end of the page. AT_END After the end tag until the scope of any enclosing tag. If there’s no enclosing tag, then to the end of the page.

JSP custom tag with dynamic attributes

Created by Fang on April 16, 2012 12:58:35 Last update: April 16, 2012 12:58:35

To implement a JSP custom tag with dynamic attributes (for example, to pass-thru arbitrary attributes not handled by the JSP tag): Set the dynamic-attributes element to true in the TLD:

<tag>
 
     <name>mark</name>
 
     <tag-class>c...

The tag handler must implement javax.servlet.jsp.tagext.DynamicAttributes :

package com.example.jsp;
 
 
 
 import java.io.*;
...

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() {...

Using tag handler, UI component and renderer with a JSF facelet taglib

Created by Fang on November 22, 2011 10:40:16 Last update: November 22, 2011 10:40:16

This is an example that uses tag handler, UI component and renderer together to support a custom taglib. The main purpose is to show how these components play together. The tag renders

<ui:param name="extra" value="el interpreted"/>
 
...

<h3>my:foreach</h3>
 
 <ul class="css class" extra...

These are the files: The tag handler ( src/main/java/com/example/ForeachTagHandler.java ):

package com.example;
 
 
 
 import java.util.Map;
...

The UI component ( src/main/java/com/example/UIForeach.java ):

package com.example;
 
 
 
 import java.io.IOExcep...

The renderer ( src/main/java/com/example/ForeachRenderer.java ):

package com.example;
 
 
 
 import java.io.IOExcep...

Faces config ( src/main/resources/META-INF/faces-config.xml ):

<?xml version="1.0" encoding="UTF-8"?>
 
 <faces-c...

Taglib config ( src/main/resources/META-INF/foreach.taglib.xml ):

<?xml version="1.0" encoding="UTF-8"?>
 
 <facelet...

JSF facelet taglib backed by a UI component

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 john steve mike 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:...

Java regex filter for HTML img tag

Created by Dr. Xi on November 11, 2011 10:05:22 Last update: November 11, 2011 10:12:01

This is an HTML image tag filter using Java regex. It takes a string, finds the img tags, replaces the src attribute with one provided by the filter, then adds a class name to the class attribute.

import java.util.regex.*;
 
 import java.io.*;
 
 ...

Test file:

<div id="HTML snippet">
 
 <img src="img/big/txt-m...

Dump binary Android xml files as plain text

Created by freyo on May 13, 2011 15:45:29 Last update: September 20, 2011 08:08:12

This is an Android app that dumps any binarized xml file as plain text - to the sdcard on the device or emulator. build.xml :

<?xml version="1.0" encoding="UTF-8"?>
 
 <project...

AndroidManifest.xml


 
 <?xml version="1.0" encoding="utf-8"?>
 
 <man...

res/layout/main.xml


 
 <?xml version="1.0" encoding="utf-8"?>
 
 <Lin...

res/values/strings.xml :


 
 <?xml version="1.0" encoding="utf-8"?>
 
 <res...

src/com/android/xmltool/DumpXml.java

package com.android.xmltool;
 
 
 
 import java.ut...

Screenshot Pre-built APK can be downloaded from: http://code.google.com/p/android-binxml-dump/

Android content provider checklist

Created by freyo on July 27, 2011 12:13:52 Last update: July 27, 2011 12:13:52

Implement the provider. Put the initialization code in onCreate , implement the necessary query and update methods. This is a skeleton:

package my.package;
 
 
 
 import android.content....

Declare the content provider in AndroidManifest.xml , with content authority (any string identifier):

<?xml version="1.0" encoding="utf-8"?>
 
 <manifes...

Use the provider (content consumer code):

// import android.content.ContentResolver;
 
 Cont...

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