{"id":50,"date":"2009-01-28T14:22:41","date_gmt":"2009-01-28T21:22:41","guid":{"rendered":"http:\/\/www.zulutown.com\/blog\/?p=50"},"modified":"2009-03-24T02:57:15","modified_gmt":"2009-03-24T09:57:15","slug":"rest-web-application-with-struts21-rest-and-convention-plugins","status":"publish","type":"post","link":"http:\/\/www.zulutown.com\/blog\/2009\/01\/28\/rest-web-application-with-struts21-rest-and-convention-plugins\/","title":{"rendered":"REST web application with Struts2.1 Rest and Convention plugins"},"content":{"rendered":"

The sample application developed in this tutorial will handle a simple message system, where it’s possible to read, add and remove messages.
\nSo, the basic bean will be defined in the Message<\/code> class:<\/p>\n

package com.zulutown.struts2.rest;\r\n\r\npublic class Message {\r\n\tprivate String id;\r\n\tprivate String text;\r\n\tprivate String author;\r\n\r\n\tpublic Message() {\r\n\t\tsuper();\r\n\t}\r\n\r\n\tpublic Message(String id, String text, String author) {\r\n\t\tsuper();\r\n\t\tthis.id = id;\r\n\t\tthis.text = text;\r\n\t\tthis.author = author;\r\n\t}\r\n\r\n\tpublic String getId() {\r\n\t\treturn id;\r\n\t}\r\n\r\n\tpublic void setId(String id) {\r\n\t\tthis.id = id;\r\n\t}\r\n\r\n\tpublic String getText() {\r\n\t\treturn text;\r\n\t}\r\n\r\n\tpublic void setText(String text) {\r\n\t\tthis.text = text;\r\n\t}\r\n\r\n\tpublic String getAuthor() {\r\n\t\treturn author;\r\n\t}\r\n\tpublic void setAuthor(String author) {\r\n\t\tthis.author = author;\r\n\t}\r\n\r\n\tpublic int hashCode() {\r\n\t\tfinal int prime = 31;\r\n\t\tint result = 1;\r\n\t\tresult = prime * result + ((id == null) ? 0 : id.hashCode());\r\n\t\treturn result;\r\n\t}\r\n\r\n\tpublic boolean equals(Object obj) {\r\n\t\tif (this == obj)\r\n\t\t\treturn true;\r\n\t\tif (obj == null)\r\n\t\t\treturn false;\r\n\t\tif (getClass() != obj.getClass())\r\n\t\t\treturn false;\r\n\t\tMessage other = (Message) obj;\r\n\t\tif (id == null) {\r\n\t\t\tif (other.id != null)\r\n\t\t\t\treturn false;\r\n\t\t} else if (!id.equals(other.id))\r\n\t\t\treturn false;\r\n\t\treturn true;\r\n\t}\r\n}<\/pre>\n
The message will be identified by the id<\/code> property and will contain its text<\/code> and its author<\/code> in the other two class properties.<\/p>\n
The next step is to setup a basic business service<\/em> that will handle the basic operations on the messages: find<\/em>, save<\/em>, remove<\/em> and so on. In a real world application this service would be a singleton that interacts with a database (through JDBC or JPA) but in this little demo the data model is just a very basic (and ugly) Map kept in a static property of the Message<\/code> class.<\/p>\n
package com.zulutown.struts2.rest;\r\n\r\nimport java.util.ArrayList;\r\nimport java.util.HashMap;\r\nimport java.util.List;\r\nimport java.util.Map;\r\n\r\npublic class MessageService {\r\n\r\n\tpublic static Map messages = new HashMap();\r\n\tprivate static int nextMessageId = 4;\r\n\r\n\tstatic {\r\n\t\tMessage message1 = new Message(\"1\", \"hello\", \"john\");\r\n\t\tMessage message2 = new Message(\"2\", \"world\", \"ted\");\r\n\t\tMessage message3 = new Message(\"3\", \"rest\", \"sam\");\r\n\t\tmessages.put(\"1\", message1);\r\n\t\tmessages.put(\"2\", message2);\r\n\t\tmessages.put(\"3\", message3);\r\n\t}\r\n\r\n\tpublic static List findAll() {\r\n\t\treturn new ArrayList(messages.values());\r\n\t}\r\n\r\n\tpublic static Message find(String id) {\r\n\t\treturn messages.get(id);\r\n\t}\r\n\r\n\tpublic static void save(Message message) {\r\n\t\tif (message.getId() == null) {\r\n\t\t\tString id = String.valueOf(nextMessageId);\r\n\t\t\tmessage.setId(id);\r\n\t\t\tnextMessageId++;\r\n\t\t}\r\n\t\tmessages.put(message.getId(), message);\r\n\t}\r\n\r\n\tpublic static void remove(String id) {\r\n\t\tmessages.remove(id);\r\n\t}\r\n}<\/pre>\n
In messages<\/code> it is stored the data and the static initializer of the MessageService<\/code> class will populate the data model with three messages.
\nThen, some utility methods are provided: findAll()<\/code> to retrieve all the messages, find(String id)<\/code> to retrieve a message with a specific id<\/code>, save(Message message)<\/code> to add (or update) a message in the data model and, finally, a remove<\/code> method to delete a specific message.<\/p>\n
Until now, this tutorial is not related at all with Struts 2.1, but now it is required to add a “web layer” to the application, and the REST capabilities provided by Struts2 will be used.<\/p>\n
The first task is to add to the Web application the .jar<\/code> libraries of Struts2. Those files must be placed into \/WEB-INF\/lib<\/code> (in WebContent) that is the standard location where a Java Web Application expects to find its dependencies.<\/p>\n
Download from the Struts website<\/a> the archives with the libraries for Struts 2.1.x (currently the GA release is 2.1.6), unpack it, and copy & paste the following jars in \/WEB-INF\/lib\/<\/code> of your project.<\/p>\n