Obtaining Commons Lang Problem You want to use Commons Lang because your program needs to use some of the simple utilities this component. Jakarta Commons Cookbook Timothy M. O’Brien Editor Brett McLaughlin Copyright © O’Reilly Media, Inc. – Selection from Jakarta Commons Cookbook. Jakarta Commons Cookbook ByTimothy M. O’Brien Publisher: O’Reilly Pub Date: November ISBN: X Table of Contents • Index • • Reviews.

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If we create the classesjakarta commons cookbook stub-out the methods, we can comkons the code to compile. In practice, the set of validations we need to pass and the command we need to run are closely coupled. If all needed attributes are defined as properties, then a ContextBase can interoperate with components that expect a Map and also with components that expect a JavaBean — all at the same time.

The Context is an envelope containing the attributes needed to complete a transaction. Many components already use a “context”. You want to cleanly separate the jakarta commons cookbook and presentation layers without complicating the jakarta commons cookbook of your application.

The Request and Response extend Context. In practice, there are usually commands within commands.

Commons Chain – Cookbook

Notice jakkarta we only pass the name jakarta commons cookbook a Command into the method. A web application may store a Profile as an attribute of the HttpSession or as a client-side “cookie”. The minus sign means remove, or subtract, the line. The path can’t be part of our chain of keys, since it is shared with the container’s “business logic”.

The Apache Struts framework is one cojmons. You want to start using Command objects in your application. Of course, the hard jakarta commons cookbook is populating the context and determining which command we need to run for a given request.


Use Test Driven Development to create a test for a Command, and let the test tell you how to write the Command. Since Commands are designed to jakarta commons cookbook on whatever Context they receive, we can create a Context with a known state to test our Command.

If a Command returns falsethen other Commands in the Chain if any may execute. Struts supports a variant of the ActionForm that utilizes a Map. Jakarta commons cookbook essence of computing might be that for any expected input Awe return the expected output B. Accordingly, we include a “Call a Command from Struts” recipe in this chapter. If the “path” needs to change to suit a change jakarta commons cookbook the JAAS configuration, nothing else needs jakarta commons cookbook change.

The Request and Response object have “name” properties. Of course, co,mons engineering decision is a trade-off. False allows a chain to continue. Since we’re using a test-first approach, we can’t run or jakarta commons cookbook compile this class yet. Also note that we retrieve the Command and pass it the Context without knowing the precise type of either object.

Using the default attribute, and given an HttpServletRequest instance, you can access the catalog by coding:. For now, we’ll cooibook return falseso that our Command could be used as part of a larger chain of Commands.

Green bar for org.

Jakarta Commons Cookbook

The Command does not know how the application stores a Profile, or even if it is stored. Most of us would do the same. The Struts Validator utilizes metadata to vet request values and create user prompts should validation fail. All references jakarta commons cookbook to the standard interfaces. Once you have access to the Catalog, the rest is easy. Even so, the path is not part of our semantic chain. Some components mix both approaches.


HandlerCommand provides default behavior that subclasses can override package org. To compile our Command and run our test, we also need a Profile class. Any of these components can be used to create a Context, access the Catalog, and execute a Command. A Catalog can be configured using jakarta commons cookbook an XML document. To test the context for type-safety, we will also need to Assign a String to jakarta commons cookbook typed property using the Map get method Confirm that the assignation throws a “type mismatch” exception.

To use ChainListener in a web application, just add a reference to your application’s web.

The test will run, but jakarta commons cookbook classes won’t pass muster. You need to create a Command for your application, so that a test of the Command will succeed. Following the general description from Core J2EE Patterns, let’s start by defining a test that passes a request to a controller and confirms that an appropriate response is returned.

A Command to create a Profile, if one coookbook exist. If jakarta commons cookbook Command changes, then its validations can change with it, without affecting other Commands.

To implement the patterns, the Chain package defines five key interfaces: Let’s implement each jakarta commons cookbook, starting with HandlerCommand, which is shown below. Many teams do the same with custom Ant build files. The Request Handler extends Command.