Recent Notes
Displaying keyword search results 1 - 10
Created by Fang on May 03, 2012 15:07:17
Last update: May 03, 2012 15:07:52
Scaling an image with default Java API loses quality (horribly!):
public static BufferedImage resizeImage(Buffer...
The imgscalr library does the job beautifully. And its' very easy to do:
// import org.imgscalr.Scalr;
public static...
To import the library in Maven:
<dependency>
<groupId>org.imgscalr</groupId>
...
Created by Fang on March 30, 2012 15:04:04
Last update: March 30, 2012 15:04:04
Spring MVC 3.1 can send either JSON or HTML response on the same URL, depending on the type of response requested. With this mechanism, a page can be sent when directly requested from a link, but a JSON response can be sent in response to an AJAX request. This is the controller code:
package com.example; import java.util.Map; ... In the above example, JSON response will be sent when the HTTP request contains header "Accept: application/json". HTML response will be sent then the header is "Accept: */*", or "Accept: text/html", or anything else. You can add a limitation that the HTML response does not produce "application/json". But then the question is which response will be sent when the HTTP header is "Accept: */*"? Both methods will...
Created by Dr. Xi on May 02, 2011 15:59:37
Last update: February 25, 2012 09:16:37
This code snippet gets the default keystore used by the Java keytool and displays the list of aliases along with the key type (certificate or private key).
import java.io.File;
import java.io.FileInputSt...
The default keystore used by the above code is: $HOME/.keystore .
Created by Dr. Xi on February 01, 2012 12:55:28
Last update: February 01, 2012 12:55:28
You can define environment variables in the Tomcat context.xml file like this:
<?xml version="1.0" encoding="UTF-8"?>
<Context...
which is equivalent to the following in web.xml :
<env-entry>
<env-entry-name>varName</env-entr...
In Java code, the variable can be looked up like this:
// import javax.naming.Context;
// import javax...
Created by Fang on January 31, 2012 16:27:39
Last update: January 31, 2012 16:27:39
Because Maven dependencies are transitive, the same artifact may be brought in with different version numbers by multiple other dependencies. For example, the current project may depend on artifact A, which in turn depends on artifact C version 1. It may also have immediate dependency on artifact B, which in turn depends on artifact C version 2. Maven resolves these version conflicts in the following ways: Dependency Mediation : If a specific version is not declared in your project POM, Maven resolves the version number by nearest definition , which means it will use the closest dependency in the tree of dependencies for the current project. When dependency depth is the same, it will pick the one that appeared in the POM first. Dependency Management...
Created by Dr. Xi on January 17, 2012 11:58:16
Last update: January 17, 2012 11:58:16
Steps to configure JavaMail resource for Tomcat 6 & 7:
Install JavaMail jar: download the JavaMail API , unzip the archive and copy mail.jar to $CATALINA_HOME/lib .
Add JavaMail resource to $CATALINA_BASE/conf/context.xml :
<?xml version="1.0"?>
<Context>
.
...
Add resource-ref for the JavaMail resource to your webapp WEB-INF/web.xml :
<?xml version="1.0" encoding="UTF-8"?>
<web-app...
Use the JavaMail resource in your webapp:
// import javax.naming.*;
// import javax.mail....
Created by Fang on December 06, 2011 19:03:25
Last update: December 07, 2011 08:54:11
Our custom tag, as implemented in the previous note , is broken when a template is used.
Create a template file ( home-template.xhtml ):
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Stric...
and a test page that uses it ( home.xhtml ):
<?xml version="1.0" encoding="UTF-8"?>
<ui:comp...
Then request the page with URL: http://localhost:8080/facelet-demo/home.jsf?name=Jack .
You'll find that our hello tag works inside ui:repeat but fails to get the value defined by ui:param ! What's the problem? Our hello tag implementation evaluated the EL with the wrong EL context!
This is the corrected implementation:
package com.example;
import java.io.IOExcep...
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"/>
...
as
<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...
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 Fang on November 10, 2011 11:27:37
Last update: November 10, 2011 11:28:25
This has been tested working with Apache MyFaces 2.1.3 running Tomcat 7.
Managed bean code:
package com.example;
import javax.faces.bea...
Facelet page:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Stric...
