How to build RESTful Web Service with Java using JAX-RS and Jersey

How to build RESTful Service with Java using JAX-RS and Jersey

Scope : Build a simple RESTful web service with using JAX-RS and Jersey.

Objective : Build an limited currency conversion RESTful service with using JAX-RS and Jersey

Requirements:

• Eclipse JAVA EE IDE
• JDK 1.6
• ApacheTomcat - 6.0.26
• The below 3 jersey related jars you have to download.
• asm-3.3.1.jar
• jersey-bundle-1.14.jar
• json.jar

Step 1: Create a dynamic web project In eclipse and named as "RestCurrencyConvertService”.

File > New > Dynamic Web Project (Select the Dynamic web module version 2.5)

Add the downloaded jars to the project build path.

Step 2: Create the service "CurrencyConvertService" class under the "com.prem.restservice" package.

/RestCurrencyConvertService/src/com/prem/restservice/CurrencyConvertService.java

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package com.prem.restservice; import javax.ws.rs.GET; import javax.ws.rs.Path; import javax.ws.rs.PathParam; import javax.ws.rs.Produces; import javax.ws.rs.core.MediaType; @Path("CurrencyConvert") public class CurrencyConvertService { @Produces(MediaType.TEXT_XML) @Path("/Convert/{from}&{to}&{amount}") @GET public String convertCurrency(@PathParam("from") String from, @PathParam("to") String to, @PathParam("amount") double amount) { // Small logic if (from.equalsIgnoreCase("USD") && to.equalsIgnoreCase("LKR")) { return "<result>" + Double.toString(amount * 130.65) + "</result>"; } else if (from.equalsIgnoreCase("LKR") && to.equalsIgnoreCase("USD")) { return "<result>" + Double.toString(amount * 0.01) + "</result>"; } else { return "<result>Invalid Currency Code...</result>"; } } }

Step 3: Add the servlet to the "web.xml" file.

The sample "web.xml" file as below.

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<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5"> <display-name>RestCurrencyConvertService</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> </welcome-file-list> <servlet> <servlet-name>CurrecnyConvert</servlet-name> <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class> <init-param> <param-name>com.sun.jersey.config.property.packages</param-name> <param-value>com.prem.restservice</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>CurrecnyConvert</servlet-name> <url-pattern>/Convert/*</url-pattern> </servlet-mapping> </web-app>

That's all folks... 

Step 4: Now the time to execute and see the result.... 

Right click on the "RestCurrencyConvertService" project and go to Run As - Run on Server.

You able to see the below screen when you paste the below URL to browser and enter.
http://localhost:8181/RestCurrencyConvertService/Convert/CurrencyConvert/Convert/USD&LKR&100

http://localhost:8181 - The "ApacheTomcat - 6.0.26" server runs on the 8181 port at my local                                             machine
/RestCurrencyConvertService - Display name in the "web.xml" file
/Convert - The url pattern defined in the "web.xml"
/CurrencyConvert - @Path("xxxxxxxx") defined in the class level
/Convert - @Path("xxxxxxxx/{from}&{to}&{amount}") defined in the method level.
/USD&LKR&100 - @Path("/Convert/{xxx}&{yyy}&{zzz}") defined in the method level.

 In this example xxx = USD, yyy = LKR and zzz = 100. 

Hope its clear...