Notes by Fang
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Created by Fang on March 30, 2012 10:07:25
Last update: March 08, 2013 13:41:57
After a user resets a password, I want to force the user to change the password before she gets access to secured content. This is usually done with a servlet filter. But with Spring MVC, you can also use a HandlerInterceptor . According to Spring JavaDoc: HandlerInterceptor is basically similar to a Servlet 2.3 Filter, but in contrast to the latter it just allows custom pre-processing with the option of prohibiting the execution of the handler itself, and custom post-processing. Filters are more powerful, for example they allow for exchanging the request and response objects that are handed down the chain. Note that a filter gets configured in web.xml, a HandlerInterceptor in the application context. As a basic guideline, fine-grained handler-related preprocessing tasks are candidates...
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.
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.*;
...
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 Fang on March 30, 2012 12:15:49
Last update: March 30, 2012 12:15:49
1. mvc:default-servlet-handler Configures a handler for serving static resources by forwarding to the Servlet container's default Servlet. Use of this handler allows using a "/" mapping with the DispatcherServlet while still utilizing the Servlet container to serve static resources. HandlerMapping: org.springframework.web.servlet.handler.SimpleUrlHandlerMapping Handler: org.springframework.web.servlet.handler.SimpleUrlHandlerMapping Attribute Description default-servlet-name The name of the default Servlet to forward to for static resource requests. The handler will try to auto-detect the container's default Servlet at startup time using a list of known names. If the default Servlet cannot be detected because of using an unknown container or because it has been manually configured, the servlet name must be set explicitly. 2. mvc:view-controller Defines a simple Controller that selects a view to render the response. HandlerMapping: org.springframework.web.servlet.handler.SimpleUrlHandlerMapping Handler: org.springframework.web.servlet.mvc.ParameterizableViewController Attribute Description...
Created by Fang on January 16, 2012 13:29:00
Last update: January 16, 2012 13:29:00
According to RFC 4627 , the MIME content type for JSON is application/json :
The MIME media type for JSON text is application/j...
So, in Java code:
servletResponse.setContentType("application/json")...
Created by Fang on January 04, 2012 11:14:46
Last update: January 04, 2012 11:14:46
Assume that your messages are defined in MessageResources.properties , this is how you load and use the messages:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Stric...
In MessageResources.properties :
pageTitle = JSF Resource Bundle Example
page.he...
Created by Fang on January 04, 2012 09:54:05
Last update: January 04, 2012 09:54:05
There are two ways to validate a form with JSF: jsf validation on the page with <f:validate...> tags (for example: <f:validateLength> , <f:validateRegex> , etc.), or JSR303 bean validation. This note is about how to customize messages for JSR303 bean validation. The validation message is specified in the message attribute for each validation annotation type. The mesage attribute is not a literal string, but a string that is interpolated in various ways. For example, the default validation message for AssertFalse is {javax.validation.constraints.AssertFalse.message} , which is replaced with the corresponding string in ValidationMessages.properties (or ValidationMessages_tr.properties , ValidationMessages_es.properties , depending on the locale). This is the contents of ValidationMessages.properties in the hibernate validator reference implementation:
javax.validation.constraints.AssertFalse.message =... To customize the messages, just provide the new value in...
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 December 03, 2011 12:31:20
Last update: December 03, 2011 12:33:23
The <h:outputText> tag generates different output for body text and value attribute. I tested the following with Apache MyFaces 2.1.3:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Stric...
With value attribute, the output was:
<table border='1' cellspacing='0' cellpadding='4'>...
With text in body, the output was (i.e., the text was escaped despite escape="false" ):
<table border='1' cellspacing='0' cellpadding='...
