Android Restful Webservice Tutorial – 2

How to create RESTFul webservice in Java?

In this post, I will be discussing about creating RESTful webservice in Java and in the next post will be discussing how to consume RESTful webservice we are about to create in Android application.

Here is the quick overview of the JEE webapp which we are going to create:

JEE webapp creation involves below steps:

1. Configure MySQL DB and Table

2. Create RESTful Webservice using Jersey

You can download source code from here if you don’t want to create Application from scratch, otherwise please proceed with below listings.

MySQL DB and Table

Do follow below steps to create MySQL DB and Table.

Create MySQL DB and Table:

1. Create database called ‘users’ in phpMyAdmin or create it through command:

   1	create database users

2. Select database users in phpMyAdmin or select it through command:

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   use users

3. Create table called ‘user’ in phpMyAdmin or through command by pasting below SQL script in SQL Query box:

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   CREATE TABLE IF NOT EXISTS ` user ` (    ` name ` varchar (50) NOT NULL ,    `username` varchar (50) NOT NULL ,    ` password ` varchar (50) NOT NULL ,    `register_dt` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ,    PRIMARY KEY (`username`) )

Jersey – RESTful Webservice

Am going to use Jersey framework to design RESTful webservice.

Reference: http://www.vogella.com/tutorials/REST/article.html#installation_jersey

Do follow the below steps to create RESTful webservice:

1. Goto https://jersey.java.net/download.html and download Jersey 1.18 ZIP bundle as shown below:Unzip the bundle, you can see list of Jars under lib folder as shown below:

2. Create Dynamic web project in Eclipse as shown below:Choose File>>New>>Dynamic Web Project

   Enter project name as ‘useraccount’ and Click Finish

3. Add unzipped Jersey library JARs to WEB-INF/lib folder

4. Register Jersey as Servlet dispatcher by adding below code into web.xml

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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 >useraccount</ display-name >    < servlet >      < servlet-name >Jersey REST Service</ 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.prgguru.jersey</ param-value >      </ init-param >      < load-on-startup >1</ load-on-startup >    </ servlet >    < servlet-mapping >      < servlet-name >Jersey REST Service</ servlet-name >      < url-pattern >/*</ url-pattern >    </ servlet-mapping > </ web-app >

5. Create a package called ‘com.prgguru.jersey’ under src folder

6. Create a class called ‘Constants.java’ under the package ‘com.prgguru.jersey’ and add below code to it:

   Constants class holds application constants like DB class, DB username etc.,

   Constants.java

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   package com.prgguru.jersey; //Change these parameters according to your DB public class Constants {      public static String dbClass = "com.mysql.jdbc.Driver" ;      private static String dbName= "users" ;      public static String dbUrl = "jdbc:mysql://localhost:3306/" +dbName;      public static String dbUser = "root" ;      public static String dbPwd = "password" ; }

7. Create a class called ‘DBConnection.java’ under the package ‘com.prgguru.jersey’ and add below code to it:

   DBConnection class performs DB related operations like Opening DB connection, Inserting records and Selecting records from Table.

   DBConnection.java

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   package com.prgguru.jersey;   import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement;   public class DBConnection {      /**       * Method to create DB Connection       *       * @return       * @throws Exception       */      @SuppressWarnings ( "finally" )      public static Connection createConnection() throws Exception {          Connection con = null ;          try {              Class.forName(Constants.dbClass);              con = DriverManager.getConnection(Constants.dbUrl, Constants.dbUser, Constants.dbPwd);          } catch (Exception e) {              throw e;          } finally {              return con;          }      }      /**       * Method to check whether uname and pwd combination are correct       *       * @param uname       * @param pwd       * @return       * @throws Exception       */      public static boolean checkLogin(String uname, String pwd) throws Exception {          boolean isUserAvailable = false ;          Connection dbConn = null ;          try {              try {                  dbConn = DBConnection.createConnection();              } catch (Exception e) {                  // TODO Auto-generated catch block                  e.printStackTrace();              }              Statement stmt = dbConn.createStatement();              String query = "SELECT * FROM user WHERE username = '" + uname                      + "' AND password=" + "'" + pwd + "'" ;              //System.out.println(query);              ResultSet rs = stmt.executeQuery(query);              while (rs.next()) {                  //System.out.println(rs.getString(1) + rs.getString(2) + rs.getString(3));                  isUserAvailable = true ;              }          } catch (SQLException sqle) {              throw sqle;          } catch (Exception e) {              // TODO Auto-generated catch block              if (dbConn != null ) {                  dbConn.close();              }              throw e;          } finally {              if (dbConn != null ) {                  dbConn.close();              }          }          return isUserAvailable;      }      /**       * Method to insert uname and pwd in DB       *       * @param name       * @param uname       * @param pwd       * @return       * @throws SQLException       * @throws Exception       */      public static boolean insertUser(String name, String uname, String pwd) throws SQLException, Exception {          boolean insertStatus = false ;          Connection dbConn = null ;          try {              try {                  dbConn = DBConnection.createConnection();              } catch (Exception e) {                  // TODO Auto-generated catch block                  e.printStackTrace();              }              Statement stmt = dbConn.createStatement();              String query = "INSERT into user(name, username, password) values('" +name+ "'," + "'"                      + uname + "','" + pwd + "')" ;              //System.out.println(query);              int records = stmt.executeUpdate(query);              //System.out.println(records);              //When record is successfully inserted              if (records > 0 ) {                  insertStatus = true ;              }          } catch (SQLException sqle) {              //sqle.printStackTrace();              throw sqle;          } catch (Exception e) {              //e.printStackTrace();              // TODO Auto-generated catch block              if (dbConn != null ) {                  dbConn.close();              }              throw e;          } finally {              if (dbConn != null ) {                  dbConn.close();              }          }          return insertStatus;      } }

8. Create a class called ‘Utility.java’ under the package ‘com.prgguru.jersey’ and add below code to it:

   Utility class has utility methods to perform Null check, contruct JSON etc.,

   Utility.java

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   package com.prgguru.jersey;   import org.codehaus.jettison.json.JSONException; import org.codehaus.jettison.json.JSONObject;   public class Utitlity {      /**       * Null check Method       *       * @param txt       * @return       */      public static boolean isNotNull(String txt) {          // System.out.println("Inside isNotNull");          return txt != null && txt.trim().length() >= 0 ? true : false ;      }        /**       * Method to construct JSON       *       * @param tag       * @param status       * @return       */      public static String constructJSON(String tag, boolean status) {          JSONObject obj = new JSONObject();          try {              obj.put( "tag" , tag);              obj.put( "status" , new Boolean(status));          } catch (JSONException e) {              // TODO Auto-generated catch block          }          return obj.toString();      }        /**       * Method to construct JSON with Error Msg       *       * @param tag       * @param status       * @param err_msg       * @return       */      public static String constructJSON(String tag, boolean status,String err_msg) {          JSONObject obj = new JSONObject();          try {              obj.put( "tag" , tag);              obj.put( "status" , new Boolean(status));              obj.put( "error_msg" , err_msg);          } catch (JSONException e) {              // TODO Auto-generated catch block          }          return obj.toString();      }   }

9. Create a class called Register.java under the package ‘com.prgguru.jersey’ and add below code to it.

   Register class is the REST resource for registering the Users. User details sent from Android application will be inserted into DB after performing necessary checks.

   Register.java

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   package com.prgguru.jersey;   import java.sql.SQLException;   import javax.ws.rs.GET; import javax.ws.rs.Path; import javax.ws.rs.Produces; import javax.ws.rs.QueryParam; import javax.ws.rs.core.MediaType; //Path: http://localhost/<appln-folder-name>/register @Path ( "/register" ) public class Register {      // HTTP Get Method      @GET      // Path: http://localhost/<appln-folder-name>/register/doregister      @Path ( "/doregister" )       // Produces JSON as response      @Produces (MediaType.APPLICATION_JSON)      // Query parameters are parameters: http://localhost/<appln-folder-name>/register/doregister?name=pqrs&username=abc&password=xyz      public String doLogin( @QueryParam ( "name" ) String name, @QueryParam ( "username" ) String uname, @QueryParam ( "password" ) String pwd){          String response = "" ;          //System.out.println("Inside doLogin "+uname+"  "+pwd);          int retCode = registerUser(name, uname, pwd);          if (retCode == 0 ){              response = Utitlity.constructJSON( "register" , true );          } else if (retCode == 1 ){              response = Utitlity.constructJSON( "register" , false , "You are already registered" );          } else if (retCode == 2 ){              response = Utitlity.constructJSON( "register" , false , "Special Characters are not allowed in Username and Password" );          } else if (retCode == 3 ){              response = Utitlity.constructJSON( "register" , false , "Error occured" );          }          return response;        }        private int registerUser(String name, String uname, String pwd){          System.out.println( "Inside checkCredentials" );          int result = 3 ;          if (Utitlity.isNotNull(uname) && Utitlity.isNotNull(pwd)){              try {                  if (DBConnection.insertUser(name, uname, pwd)){                      System.out.println( "RegisterUSer if" );                      result = 0 ;                  }              } catch (SQLException sqle){                  System.out.println( "RegisterUSer catch sqle" );                  //When Primary key violation occurs that means user is already registered                  if (sqle.getErrorCode() == 1062 ){                      result = 1 ;                  }                  //When special characters are used in name,username or password                  else if (sqle.getErrorCode() == 1064 ){                      System.out.println(sqle.getErrorCode());                      result = 2 ;                  }              }              catch (Exception e) {                  // TODO Auto-generated catch block                  System.out.println( "Inside checkCredentials catch e " );                  result = 3 ;              }          } else {              System.out.println( "Inside checkCredentials else" );              result = 3 ;          }            return result;      }   }

10. Create a class called ‘Login.java’ under the package ‘com.prgugur.jersey’ and add below code to it.

    Login class is the REST resource which authenticates the Users. It gets the User credentials sent from Android application through HTTP and authenticates whether the credential is valid or not.

    Login.java

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    package com.prgguru.jersey;   import javax.ws.rs.GET; import javax.ws.rs.Path; import javax.ws.rs.Produces; import javax.ws.rs.QueryParam; import javax.ws.rs.core.MediaType; //Path: http://localhost/<appln-folder-name>/login @Path ( "/login" ) public class Login {      // HTTP Get Method      @GET      // Path: http://localhost/<appln-folder-name>/login/dologin      @Path ( "/dologin" )      // Produces JSON as response      @Produces (MediaType.APPLICATION_JSON)      // Query parameters are parameters: http://localhost/<appln-folder-name>/login/dologin?username=abc&password=xyz      public String doLogin( @QueryParam ( "username" ) String uname, @QueryParam ( "password" ) String pwd){          String response = "" ;          if (checkCredentials(uname, pwd)){              response = Utitlity.constructJSON( "login" , true );          } else {              response = Utitlity.constructJSON( "login" , false , "Incorrect Email or Password" );          }      return response;             }        /**       * Method to check whether the entered credential is valid       *       * @param uname       * @param pwd       * @return       */      private boolean checkCredentials(String uname, String pwd){          System.out.println( "Inside checkCredentials" );          boolean result = false ;          if (Utitlity.isNotNull(uname) && Utitlity.isNotNull(pwd)){              try {                  result = DBConnection.checkLogin(uname, pwd);                  //System.out.println("Inside checkCredentials try "+result);              } catch (Exception e) {                  // TODO Auto-generated catch block                  //System.out.println("Inside checkCredentials catch");                  result = false ;              }          } else {              //System.out.println("Inside checkCredentials else");              result = false ;          }            return result;      }   }

11. Deploy the web application:Right click on the project ‘useraccount’ >> Run As >> Run on Server

Code Dissection

Here are the important annotations in Jersey.

Annotation	Description
@PATH(your_path)	Sets the path to base URL + /your_path. The base URL is based on your application name, the servlet and the URL pattern from the web.xml configuration file.
@POST	Indicates that the following method will answer to an HTTP POST request.
@GET	Indicates that the following method will answer to an HTTP GET request.
@PUT	Indicates that the following method will answer to an HTTP PUT request.
@DELETE	Indicates that the following method will answer to an HTTP DELETE request.
@Produces(MediaType.TEXT_PLAIN[, more-types])	@Produces defines which MIME type is delivered by a method annotated with @GET. In the example text (「text/plain」) is produced. Other examples would be 「application/xml」 or 「application/json」.
@Consumes(type[, more-types])	@Consumes defines which MIME type is consumed by this method.
@PathParam	Used to inject values from the URL into a method parameter. This way you inject, for example, the ID of a resource into the method to get the correct object.

Login.java

This class has a method called ‘doLogin’ which is the REST resource, that accepts query parameters as parameters and produce JSON as the response. Query parameters are Username and Password that are used for Authenticating the Users.

URL path to the method ‘dologin’ is illustrated in the below image:

Register.java

This class has a method called ‘doregister’ which is the REST resource, that accepts query parameters as parameters and produce JSON as the response.

URL path to the method ‘doregister’ is illustrated in the below image:

Install Chrome Advanced REST client extension for Testing

Chrome Advanced REST client extension provides an easy way to test the REST API. It provides lot of options like adding request headers, adding request parameters, changing HTTP method by hitting an url. Install Advanced REST clientextension in chrome browser and once you installed it you can find it in chrome Apps or an icon at the top right corner.

Registration

URL for registering the User is http://192.168.2.4:9999/useraccount/register/doregister?name=Admin&username=admin@programmerguru.com&password=password. Make sure you changed the IP address to your LAN IP address.

Logging in

URL for logging in the User is http://192.168.2.4:9999/useraccount/register/doregister?username=admin@programmerguru.com&password=password. Make sure you changed the IP address to your LAN IP address.