Restful web services_tutorial
- 2. RESTful Web Services i AbouttheTutorial RESTful Web Services are basically REST Architecture based Web Services. In REST Architecture everything is a resource. RESTful web services are light weight, highly scalable and maintainable and are very commonly used to create APIs for web-based applications. This tutorial will teach you the basics of RESTful Web Services and contains chapters discussing all the basic components of RESTful Web Services with suitable examples. Audience This tutorial is designed for Software Professionals who are willing to learn RESTful Web Services in simple and easy steps. This tutorial will give you great understanding on RESTful Web Services concepts and after completing this tutorial you will be at intermediate level of expertise from where you can take yourself at higher level of expertise. Prerequisites Before proceeding with this tutorial, you should have a basic understanding of Java Language, Text Editor, etc. Because we are going to develop web services applications using RESTful, so it will be good if you have understanding on other web technologies like HTML, CSS, AJAX, etc. Copyright&Disclaimer Copyright 2016 by Tutorials Point (I) Pvt. Ltd. All the content and graphics published in this e-book are the property of Tutorials Point (I) Pvt. Ltd. The user of this e-book is prohibited to reuse, retain, copy, distribute or republish any contents or a part of contents of this e-book in any manner without written consent of the publisher. We strive to update the contents of our website and tutorials as timely and as precisely as possible, however, the contents may contain inaccuracies or errors. Tutorials Point (I) Pvt. Ltd. provides no guarantee regarding the accuracy, timeliness or completeness of our website or its contents including this tutorial. If you discover any errors on our website or in this tutorial, please notify us at [email protected]
- 3. RESTful Web Services ii TableofContents About the Tutorial ............................................................................................................................................i Audience...........................................................................................................................................................i Prerequisites.....................................................................................................................................................i Copyright & Disclaimer .....................................................................................................................................i Table of Contents.............................................................................................................................................ii 1. RESTFUL WEB SERVICES – INTRODUCTION...........................................................................1 What is REST?..................................................................................................................................................1 RESTFul Web Services......................................................................................................................................1 Creating RESTFul Web Service .........................................................................................................................1 2. RESTFUL WEB SERVICES – ENVIRONMENT SETUP ................................................................3 Setup Java Development Kit (JDK) ...................................................................................................................3 Setup Eclipse IDE .............................................................................................................................................3 Setup Jersey Framework Libraries ...................................................................................................................4 Setup Apache Tomcat......................................................................................................................................5 3. RESTFUL WEB SERVICES – FIRST APPLICATION.....................................................................7 Creating a Java Project.....................................................................................................................................7 Creating the Source Files..................................................................................................................................9 Creating the Web.xml configuration File........................................................................................................13 4. RESTFUL WEB SERVICES – RESOURCES...............................................................................16 What is a Resource?.......................................................................................................................................16 5. RESTFUL WEB SERVICES – MESSAGES ................................................................................18 6. RESTFUL WEB SERVICES – ADDRESSING.............................................................................21 7. RESTFUL WEB SERVICES – METHODS .................................................................................22
- 4. RESTful Web Services iii Testing the Web Service ................................................................................................................................31 8. RESTFUL WEB SERVICES – STATELESSNESS.........................................................................35 9. RESTFUL WEB SERVICES – CACHING...................................................................................36 10. RESTFUL WEB SERVICES – SECURITY...............................................................................38 11. RESTFUL WEB SERVICES – JAVA (JAX-RS).........................................................................40 Specifications.................................................................................................................................................40
- 5. RESTful Web Services 1 WhatisREST? REST stands for REpresentational State Transfer. REST is a web standards based architecture and uses HTTP Protocol for data communication. It revolves around resources where every component is a resource and a resource is accessed by a common interface using HTTP standard methods. REST was first introduced by Roy Fielding in year 2000. In REST architecture, a REST Server simply provides access to resources and the REST client accesses and presents the resources. Here each resource is identified by URIs/ Global IDs. REST uses various representations to represent a resource like Text, JSON and XML. JSON is now the most popular format being used in Web Services. HTTP Methods The following HTTP methods are most commonly used in a REST based architecture. GET - Provides a read only access to a resource. PUT - Used to create a new resource. DELETE - Used to remove a resource. POST - Used to update an existing resource or create a new resource. OPTIONS - Used to get the supported operations on a resource. RESTFulWebServices A web service is a collection of open protocols and standards used for exchanging data between applications or systems. Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer. This interoperability (e.g., between Java and Python, or Windows and Linux applications) is due to the use of open standards. Web services based on REST Architecture are known as RESTful Web Services. These web services use HTTP methods to implement the concept of REST architecture. A RESTful web service usually defines a URI (Uniform Resource Identifier), which is a service that provides resource representation such as JSON and a set of HTTP Methods. CreatingRESTFulWebService In this tutorial, we will create a web service called User Management with the following functionalities: 1. RESTful Web Services – Introduction
- 6. RESTful Web Services 2 Sr. No. HTTP Method URI Operation Operation Type 1 GET /UserService/users Get list of users Read Only 2 GET /UserService/users/1 Get User with Id 1 Read Only 3 PUT /UserService/users/2 Insert User with Id 2 Idempotent 4 POST /UserService/users/2 Update User with Id 2 N/A 5 DELETE /UserService/users/1 Delete User with Id 1 Idempotent 6 OPTIONS /UserService/users List the supported operations in web service Read Only
- 7. RESTful Web Services 3 This tutorial will guide you on how to prepare a development environment to start your work with Jersey Framework to create RESTful Web Services. Jersey framework implements JAX-RS 2.0 API, which is a standard specification to create RESTful Web Services. This tutorial will also teach you how to setup JDK, Tomcat and Eclipse on your machine before you the Jersey Framework is setup. SetupJavaDevelopmentKit(JDK) You can download the latest version of SDK from Oracle's Java site: Java SE Downloads. You will find the instructions for installing JDK in the downloaded files. Follow the given instructions to install and configure the setup. Finally set the PATH and JAVA_HOME environment variables to refer to the directory that contains Java and Javac, typically java_install_dir/bin and java_install_dir respectively. If you are running Windows and installed the JDK in C:jdk1.7.0_75, you would have to put the following line in your C:autoexec.bat file. set PATH=C:jdk1.7.0_75bin;%PATH% set JAVA_HOME=C:jdk1.7.0_75 Alternatively, on Windows NT/2000/XP, you could also right-click on My Computer select Properties then Advanced then Environment Variables. Then, you would update the PATH value and press the OK button. On Unix (Solaris, Linux, etc.), if the SDK is installed in /usr/local/jdk1.7.0_75 and you use the C Shell, you would put the following into your .cshrc file. setenv PATH /usr/local/jdk1.7.0_75/bin:$PATH setenv JAVA_HOME /usr/local/jdk1.7.0_75 Alternatively, if you use an Integrated Development Environment (IDE) like Borland JBuilder, Eclipse, IntelliJ IDEA, or Sun ONE Studio, compile and run a simple program to confirm that the IDE knows where you installed Java, otherwise do proper setup as given document of the IDE. SetupEclipseIDE All the examples in this tutorial have been written using the Eclipse IDE. So, I would suggest you should have the latest version of Eclipse installed on your machine. To install Eclipse IDE, download the latest Eclipse binaries from http://www.eclipse.org/downloads/. Once you downloaded the installation, unpack the binary distribution to a convenient location. For example, in C:eclipse on windows, or /usr/local/eclipse on Linux/Unix and finally set the PATH variable appropriately. Eclipse can be started by executing the following commands on a windows machine, or you can simply double click on eclipse.exe 2. RESTful Web Services – Environment Setup
- 8. RESTful Web Services 4 %C:eclipseeclipse.exe Eclipse can be started by executing the following commands on Unix (Solaris, Linux, etc.) machine: $/usr/local/eclipse/eclipse After a successful startup, if everything is fine, then your screen should display the following result: SetupJerseyFrameworkLibraries Now, if everything is fine, then you can proceed to setup the Jersey framework. Following are a few simple steps to download and install the framework on your machine. Make a choice whether you want to install Jersey on Windows, or Unix and then proceed to the next step to download the .zip file for windows and then the .tz file for Unix. Download the latest version of Jersey framework binaries from the following link – https://jersey.java.net/download.html. At the time of writing this tutorial, I downloaded jaxrs-ri-2.17.zip on my Windows machine and when you unzip the downloaded file it will give you the directory structure inside E:jaxrs-ri-2.17jaxrs-ri as shown in the following screenshot.
- 9. RESTful Web Services 5 You will find all the Jersey libraries in the directories C:jaxrs-ri-2.17jaxrs-rilib and dependencies in C:jaxrs-ri-2.17jaxrs-riext. Make sure you set your CLASSPATH variable on this directory properly otherwise you will face problem while running your application. If you are using Eclipse, then it is not required to set the CLASSPATH because all the settings will be done through Eclipse. SetupApacheTomcat You can download the latest version of Tomcat from http://tomcat.apache.org/. Once you downloaded the installation, unpack the binary distribution into a convenient location. For example in C:apache-tomcat-7.0.59 on windows, or /usr/local/apache-tomcat-7.0.59 on Linux/Unix and set CATALINA_HOME environment variable pointing to the installation locations. Tomcat can be started by executing the following commands on a windows machine, or you can simply double click on startup.bat. %CATALINA_HOME%binstartup.bat or C:apache-tomcat-7.0.59binstartup.bat Tomcat can be started by executing the following commands on a Unix (Solaris, Linux, etc.) machine: $CATALINA_HOME/bin/startup.sh or /usr/local/apache-tomcat-7.0.59/bin/startup.sh After a successful startup, the default web applications included with Tomcat will be available by visiting http://localhost:8080/. If everything is fine then it should display the following result:
- 10. RESTful Web Services 6 Further information about configuring and running Tomcat can be found in the documentation included on this page. This information can also be found on the Tomcat website: http://tomcat.apache.org. Tomcat can be stopped by executing the following commands on a windows machine: %CATALINA_HOME%binshutdown or C:apache-tomcat-7.0.59binshutdown Tomcat can be stopped by executing the following commands on Unix (Solaris, Linux, etc.) machine: $CATALINA_HOME/bin/shutdown.sh or /usr/local/apache-tomcat-7.0.59/bin/shutdown.sh Once you are done with this last step, you are ready to proceed for your first Jersey example which you will see in the next chapter.
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