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Created by voodoo on August 03, 2012 08:42:38
Last update: August 03, 2012 09:31:25
The C function getsockopt lets you get the error codes with the option SO_ERROR . The possible error numbers are defined in the global errno.h . The relevant values are:
#define ETIMEDOUT 110 /* Connection timed out */
...
But here's the whole list on my Linux system ( /usr/include/asm-generic/errno.h ):
#ifndef _ASM_GENERIC_ERRNO_H
#define _ASM_GENER...
Created by zhidao on April 25, 2012 14:56:38
Last update: April 25, 2012 14:56:38
Lacking better alternatives, this is how I render a global validation error:
<spring:bind path="changePasswordForm">
<c:if ...
<form:errors> without path attribute seems to work too:
<form:errors cssClass="ui-error"/>
Created by zhidao on January 23, 2012 15:00:19
Last update: January 23, 2012 15:00:19
The domain object is annotated @Entity , but Java runtime complains that it's not an entity class.
Cause: : class not listed in persistence.xml , or persistence.xml misplaced, or multiple persistence.xml files existed.
Created by zhidao on January 23, 2012 14:58:58
Last update: January 23, 2012 14:58:58
This exception occurs when the Java object attribute is of type String, while the database column is of type CHAR(n), and hibernate.hbm2ddl.auto is validate in persistence.xml .
There are two solutions:
Add columnDefinition to the @Column annotation:
@Column(name = “STATE_CODE”, columnDefinition = “c...
Remove hibernate.hbm2ddl.auto from persistence.xml .
Created by Fang on November 12, 2011 21:03:03
Last update: November 12, 2011 21:03:03
Experts may disagree but I found it absolutely stunning that JSF EL does not provide an operator for string concatenation. The Java "+" operator is there for the take. Java, which is a strongly typed compiled language, overloads the "+" operator in such a way that any object can be concatenated with a string. But JSF EL, which definitely isn't as strongly typed as Java, restricts the "+" operator to numerical values only! Of course, experts may argue that the "+" operator overloading is a huge design flaw of the Java language. But even so, JSF EL is not the right place to fix it! In some cases, a concatenation operator isn't needed, for example:
<ui:repeat var="tab" value="#{tabs}"> <img ... But in case the concatenated...
Created by Dr. Xi on July 11, 2011 12:24:10
Last update: July 11, 2011 12:25:44
This code snippet
import java.util.*;
public class UncheckedCast ...
fails with a compilation error and a warning:
$ javac -Xlint:unchecked UncheckedCast.java
Unc...
Because List<String> is not a reifiable type, the Java Runtime does not have enough information to verify the type or do the type casting. This is fixed by changing List<String> to List<?> (or to the raw type List ):
public static void main(String[] args) {
Ob...
Created by alfa on May 26, 2011 13:23:30
Last update: May 26, 2011 13:23:30
The operator instanceof returns true if the first operand is an instance of the second operand:
if (a instanceof A) {
// true if a is an in...
If the above is true, then this is also true:
A.class.isAssignableFrom(a.getClass());
The only difference is, the second operand to instanceof is the symbol for a class, not a class object:
// This is OK
if (a instanceof A) {
Syst...
Created by jinx on May 03, 2011 11:43:26
Last update: May 03, 2011 11:43:26
The PHP function strval returns the string value of a variable. It does the same thing as casting a variable to string, or automatic conversion where string is expected.
Conversion rules:
Type String Value
Boolean TRUE '1'
Boolean FALSE '' (empty string)
integer of float string representing the number
Array The string 'Array'
Object Result of __toString() if defined, error otherwise
Resource 'Resource id #n' , where n is a number assigned to the resource.
NULL '' (empty string)
Example:
<?php
set_error_handler(function($errno, $errst...
Results:
bool(true)
---------------------
strval: '1'...
Created by jinx on April 26, 2011 21:52:10
Last update: April 26, 2011 21:52:10
PHP offers several ways to check the class type of an object instance at runtime: instanceof operator, is_a function, get_class function.
Example:
<?php
class A {
}
class B {
}
...
Created by jinx on April 25, 2011 12:43:40
Last update: April 25, 2011 12:43:40
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';
...
