In the test for the simple taglib example , I used a literal string for the name attribute: <my:hello name="Jack"/> What happens if the name attribute contains EL expresson? For example: <my:hello name="#{param['name']}"/> If EL works, the tag should take the value of the " name " request parameter and print it out. But the tag as implemented in the simple taglib example prints the literal string: Hello #{param['name']}! I am FaceletTag. In order to make a tag to recognize EL, we have to use TagAttribute.getValue(FaceletContext ctx) instead of TagAttribute.getValue() . The latter returns the literal value of the attribute. The HelloTagHandler should be changed to: package com.example; import java.io.IOExcep... Rebuild the taglib and test with a URL like this: http://localhost:8080/facelet-test/?name=Jack The tag will print:...

This is an example that uses dynamic proxies to trace method calls (in logging) and print out elapsed times for them. Because dynamic proxies can only be generated for interfaces, the service classes must be implemented with interface-implementation pairs. Create services A and B. A.java : public interface A { public void service1()... AImpl.java : import java.util.Random; public class AImpl... B.java : public interface B { public void service1()... BImpl.java : public class BImpl implements B { public vo... The call trace proxy: import java.lang.reflect.*; class TraceProx... The performance proxy: import java.lang.reflect.*; class Performan... The service factory: import java.lang.reflect.*; public class Se... The test class: public class Test { public static void main... The output: Entering AImpl.service1 Entering BImpl.service1... The above example has no information...

Dynamic proxy can be used to eliminate the need to stub out unused interface methods. This is an example for a simple SAX content handler for XML parsing. The org.xml.sax.ContentHandler interface requires 11 methods be implemented but we only need three: import java.io.IOException; import java.util.Ar... With a dynamic proxy, we don't need the empty blocks for the unused methods: import java.io.IOException; import java.util.Ar... Equivalently (with anonymous inner class): import java.io.IOException; import java.util.Ar... demo.xml : <breakfast-menu> <food> <name>Belgian W...

The String.format() method provides versatile formatting capabilities. This tutorial tries to present these capabilities in a accessible manner. The format string A format string can contain zero, one, or more format specifiers . The general form of a format specifier is: %[argument_index$] [flags] [width] [.precision]co... where things in square brackets are optional, and conversion is a character indicating the conversion to be applied to the corresponding variable value. The only required characters in the format specifier is the percent sign % and the conversion character. A simple example: public static void simpleFormat() { System.out... The Argument index The argument index is specified by a number, terminated by the dollar sign $ . The same argument may be repeated multiple times in a format string. Unindexed...

Use the PHP function method_exists to check if the class or object has a certain method. It returns TRUE if the method exists (even when the value of the property is NULL), FALSE if the method does not exist. Example: <?php class A { var $p = 'A property'; ... Outputs: Class A has method f1: bool(true) Object $a has... Also note that C++-like method overloading does not exist in PHP. Thus there's no ambiguity about which version of the method exists, i.e., with no argument, with one argument... etc. The following code generates Fatal error: <?php class A { var $p = 'A property'; ...

Python defines a long list of special methods to customize class behavior. This is a short list for the Basic Customizations . Method Description object.__new__(cls[, ...]) Called to create a new instance of class cls. __new__() is a static method (special-cased so you need not declare it as such) that takes the class of which an instance was requested as its first argument. __new__() is intended mainly to allow subclasses of immutable types (like int, str, or tuple) to customize instance creation. It is also commonly overridden in custom metaclasses in order to customize class creation. object.__init__(self[,...]) Called when the instance is created. The arguments are those passed to the class constructor expression. If a base class has an __init__() method, the derived class’s __init__()...

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...

This note demonstrates a technique to load a module generated at runtime, whose name is pre-determined but path is created at runtime. Sample module code: # DO NOT EDIT! # This module is generated at ru... Method one (use require ): C:\>perl $rpath = 'runtimepath'; require "${... Method two (use use with eval ): C:\>perl $rpath = 'runtimepath'; eval("use l...

For old-style classes: BaseClassName.methodname(self, arguments) >>> class A: ... def hello(self): ... ... For new-style class (any class which inherits from object ): super(ClassName, self).method(args) >>> class M(object): ... def hello(self): ... Reference: Things to Know About Python Super

The HTML page <!DOCTYPE html> <html> <head> <title>jQu... Client Side Code // called before upload submit function sta... Server Side Code Using Apache Commons FileUpload as example. Upload code (responds to fileUpload.do ): final HttpSession session = httpServletRequest... Progress code (responds to uploadProgress.do ): HttpSession session = httpServletRequest.getSe...

This is an Ant custom task to merge Properties files I lifted from http://marc.info/?l=ant-user&m=106442688632164&w=2 , with some minor bug fixes. Example usage: <taskdef name="mergeProperty" classname="ant.task.... Implementation: package ant.task.addon; import java.io.Buff...