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Chapter 29: Introduction to Web Services and SOAP

Chapter 29: Introduction to Web Services and SOAP. Outline 29.1 Introduction 29.2 Simple Object Access Protocol (SOAP) 29.3 SOAP Weather Service. 29.1 Introduction. SOAP Simple Object Access Protocol Promote interoperability Communication among different software systems.

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Chapter 29: Introduction to Web Services and SOAP

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  1. Chapter 29: Introduction to Web Services and SOAP Outline29.1 Introduction29.2 Simple Object Access Protocol (SOAP)29.3 SOAP Weather Service

  2. 29.1 Introduction • SOAP • Simple Object Access Protocol • Promote interoperability • Communication among different software systems. • Provides XML communication in many Web services • Web Services • Exposes public interfaces usable by Web applications

  3. 29.2 Simple Object Access Protocol (SOAP) • SOAP • HTTP-XML-based protocol • Enables application to communicate over Internet • Uses XML documents called messages • SOAP message contains an envelope • Describes message’s content and intended recipient • Ability to make a Remote Procedure Call (RPC) • Request to another machine to run a task

  4. Class SimpleService resides on a server Method returns a String when invoked; this method is made available to remote clients 1 // Fig. 29.1: SimpleService.java 2 // Implementation for the requested method on the server 3 4 public class SimpleService { 5 6 public String getWelcome( String message ) throws Exception 7 { 8 String text = 9 "Welcome to SOAP!\nHere is your message: " + message; 10 11 return text; // response 12 } 13 } Fig. 29.1 ClassSimpleService.Line 4Lines 6-12

  5. 29.2 Simple Object Access Protocol (SOAP) (cont.) Fig. 29.2 SOAP package administration tool.

  6. 29.2 Simple Object Access Protocol (SOAP) (cont.) Fig. 29.3 Description of deployed service.

  7. SOAP-implementation APIs Client for the RPC Specify encoding style used for SOAP message Specify URL of server to which the client sends the SOAP message Instantiate Call object and set its URI 1 // Fig. 29.4 : GetMessage.java 2 // Program that makes a SOAP RPC 3 4 // import Java packages 5 import java.io.*; 6 import java.net.*; 7 import java.util.*; 8 9 // import third-party packages 10 import org.apache.soap.*; 11 import org.apache.soap.rpc.*; 12 13 public class GetMessage { 14 15 // main method 16 public static void main( String args[] ) { 17 String encodingStyleURI = Constants.NS_URI_SOAP_ENC; 18 String message; 19 20 if ( args.length != 0 ) 21 message = args[ 0 ]; 22 else 23 message = "Thanks!"; 24 25 // attempt SOAP remote procedure call 26 try { 27 URL url = new URL( 28 "http://localhost:8080/soap/servlet/rpcrouter" ); 29 30 // build call 31 Call remoteMethod = new Call(); 32 remoteMethod.setTargetObjectURI( 33 "urn:xml-simple-message" ); 34 Fig. 29.4 Client making a SOAP request (part 1).Lines 10-11Line 13Line 17Lines 27-28Lines 31-33

  8. Build parameters used to invoke method getWelcome of class SimpleService Invoke method getWelcome and store returned value in Response object Display message if error occurred Display remote method’s returned value if no problems occurred 35 // set name of remote method to be invoked 36 remoteMethod.setMethodName( "getWelcome" ); 37 remoteMethod.setEncodingStyleURI( encodingStyleURI ); 38 39 // set parameters for remote method 40 Vector parameters = new Vector(); 41 42 parameters.addElement( new Parameter( "message", 43 String.class, message, null ) ); 44 remoteMethod.setParams( parameters ); 45 Response response; 46 47 // invoke remote method 48 response = remoteMethod.invoke( url, "" ); 49 50 // get response 51 if ( response.generatedFault() ) { 52 Fault fault = response.getFault(); 53 54 System.err.println( "CALL FAILED:\nFault Code = " 55 + fault.getFaultCode()+ "\nFault String = " 56 + fault.getFaultString() ); 57 } 58 59 else { 60 Parameter result = response.getReturnValue(); 61 62 // display result of call 63 System.out.println( result.getValue() ); 64 } 65 } 66 Fig. 29.4 Client making a SOAP request (part 2).Lines 40-44Line 48Lines 51-57Lines 60-63

  9. 67 // catch malformed URL exception 68 catch ( MalformedURLException malformedURLException ) { 69 malformedURLException.printStackTrace(); 70 System.exit( 1 ); 71 } 72 73 // catch SOAPException 74 catch ( SOAPException soapException ) { 75 System.err.println( "Error message: " + 76 soapException.getMessage() ); 77 System.exit( 1 ); 78 } 79 } 80 } Fig. 29.4 Client making a SOAP request (part 3). java GetMessage Welcome to SOAP!Here is your message: Thanks! java GetMessage "my message”Welcome to SOAP!Here is your message: my message

  10. 29.3 SOAP Weather Service • SOAP Weather Service • Web service • Modification of RMI-based Weather Service (Chapter 13) • Use SOAP RPC instead of Java RMI • Send information from server to client

  11. Class WeatherService provides method getWeatherInformation that class WeatherServiceClient calls through SOAP RPC 1 // Fig. 29.5: WeatherService.java 2 // WeatherService provides a method to retrieve weather 3 // information from the National Weather Service. 4 package com.deitel.advjhtp1.soap.weather; 5 6 // Java core packages 7 import java.io.*; 8 import java.net.URL; 9 import java.util.*; 10 11 publicclass WeatherService { 12 13 private Vector weatherInformation; // WeatherBean objects 14 15 // get weather information from NWS 16 privatevoid updateWeatherConditions() 17 { 18 try { 19 System.out.println( "Update weather information..." ); 20 21 // National Weather Service Travelers Forecast page 22 URL url = new URL( 23 "http://iwin.nws.noaa.gov/iwin/us/traveler.html" ); 24 25 // set up text input stream to read Web page contents 26 BufferedReader in = new BufferedReader( 27 new InputStreamReader( url.openStream() ) ); 28 29 // helps determine starting point of data on Web page 30 String separator = "TAV12"; 31 32 // locate separator string in Web page 33 while ( !in.readLine().startsWith( separator ) ) 34 ; // do nothing 35 Fig. 29.5 SOAP implementation of class Weather-Service (part 1).Line 11

  12. Add Strings parsed from Traveler’s Forecast Web page to Vector 36 // strings representing headers on Travelers Forecast 37 // Web page for daytime and nighttime weather 38 String dayHeader = 39 "CITY WEA HI/LO WEA HI/LO"; 40 String nightHeader = 41 "CITY WEA LO/HI WEA LO/HI"; 42 43 String inputLine = ""; 44 45 // locate header that begins weather information 46 do { 47 inputLine = in.readLine(); 48 } while ( !inputLine.equals( dayHeader ) && 49 !inputLine.equals( nightHeader ) ); 50 51 weatherInformation = new Vector(); // create Vector 52 53 // create WeatherBeans containing weather data and 54 // store in weatherInformation Vector 55 inputLine = in.readLine(); // get first city's data 56 57 // The portion of inputLine containing relevant data 58 // is 28 characters long. If the line length is not at 59 // least 28 characters long, then done processing data. 60 while ( inputLine.length() > 28 ) { 61 62 // Prepare strings for WeatherBean for each city. 63 // First 16 characters are city name. Next, six 64 // characters are weather description. Next six 65 // characters are HI/LO or LO/HI temperature. 66 weatherInformation.add( 67 inputLine.substring( 0, 16 ) ); 68 weatherInformation.add( 69 inputLine.substring( 16, 22 ) ); Fig. 29.5 SOAP implementation of class Weather-Service (part 2).Lines 66-71

  13. Method getWeatherInformation is made available to remote clients 70 weatherInformation.add( 71 inputLine.substring( 23, 29 ) ); 72 73 inputLine = in.readLine(); // get next city's data 74 } 75 76 in.close(); // close connection to NWS Web server 77 78 System.out.println( "Weather information updated." ); 79 } 80 81 // process failure to connect to National Weather Service 82 catch( java.net.ConnectException connectException ) { 83 connectException.printStackTrace(); 84 System.exit( 1 ); 85 } 86 87 // process other exceptions 88 catch( Exception exception ) { 89 exception.printStackTrace(); 90 System.exit( 1 ); 91 } 92 } 93 94 // implementation for WeatherService interface method 95 public Vector getWeatherInformation() 96 { 97 updateWeatherConditions(); 98 99 return weatherInformation; 100 } 101 } Fig. 29.5 SOAP implementation of class Weather-Service (part 3).Lines 95-100

  14. Set SOAP service’s URL 1 // Fig. 29.6: WeatherServiceClient.java 2 // WeatherServiceClient accesses the WeatherService remote 3 // object via SOAP to retrieve weather information. 4 package com.deitel.advjhtp1.soap.weather; 5 6 // Java core packages 7 import java.util.*; 8 import java.net.*; 9 10 // Java extension packages 11 import javax.swing.*; 12 13 // third-party packages 14 import org.apache.soap.*; 15 import org.apache.soap.rpc.*; 16 17 // Deitel packages 18 import com.deitel.advjhtp1.rmi.weather.*; 19 20 publicclass WeatherServiceClient extends JFrame { 21 22 // WeatherServiceClient constructor 23 public WeatherServiceClient( String server ) 24 { 25 super( "SOAP WeatherService Client" ); 26 27 // connect to server and get weather information 28 try { 29 30 // URL of remote SOAP object 31 URL url = new URL( "http://" + server + ":8080/soap/" 32 + "servlet/rpcrouter" ); 33 Fig. 29.6 SOAP implementation of class Weather-ServiceClient (part 1).Lines 31-32

  15. Instantiate Call object and set its URI Invoke remote method getWeatherInfomation and store returned value in Response object Display message if error occurred Display remote method’s returned value as List if no problems occurred 34 // build SOAP RPC call 35 Call remoteMethod = new Call(); 36 remoteMethod.setTargetObjectURI( 37 "urn:xml-weather-service" ); 38 39 // set name of remote method to be invoked 40 remoteMethod.setMethodName( 41 "getWeatherInformation" ); 42 remoteMethod.setEncodingStyleURI( 43 Constants.NS_URI_SOAP_ENC ); 44 45 // invoke remote method 46 Response response = remoteMethod.invoke( url, "" ); 47 48 // get response 49 if ( response.generatedFault() ) { 50 Fault fault = response.getFault(); 51 52 System.err.println( "CALL FAILED:\nFault Code = " 53 + fault.getFaultCode() + "\nFault String = " 54 + fault.getFaultString() ); 55 } 56 57 else { 58 Parameter result = response.getReturnValue(); 59 60 Vector weatherStrings = ( Vector ) 61 result.getValue(); 62 63 // get weather information from result object 64 List weatherInformation = createBeans( 65 weatherStrings ); 66 Fig. 29.6 SOAP implementation of class Weather-ServiceClient (part 2).Lines 35-37Line 46Lines 49-55Lines 58-65

  16. Covert Vector of Strings to List of WeatherBeans 67 // create WeatherListModel for weather information 68 ListModel weatherListModel = 69 new WeatherListModel( weatherInformation ); 70 71 // create JList, set its CellRenderer and add to 72 // layout 73 JList weatherJList = new JList( weatherListModel ); 74 weatherJList.setCellRenderer( new 75 WeatherCellRenderer() ); 76 getContentPane().add( new 77 JScrollPane( weatherJList ) ); 78 } 79 80 } // end try 81 82 // handle bad URL 83 catch ( MalformedURLException malformedURLException ) { 84 malformedURLException.printStackTrace(); 85 } 86 87 // handle SOAP exception 88 catch ( SOAPException soapException ) { 89 soapException.printStackTrace(); 90 } 91 92 } // end WeatherServiceClient constructor 93 94 // create List of WeatherBeans from Vector of Strings 95 public List createBeans( Vector weatherStrings ) 96 { 97 List list = new ArrayList(); Fig. 29.6 SOAP implementation of class Weather-ServiceClient (part 3).Line 95

  17. 98 for ( int i = 0; ( weatherStrings.size() - 1 ) > i; 99 i += 3 ) { 100 list.add( new WeatherBean( 101 ( String ) weatherStrings.elementAt( i ), 102 ( String ) weatherStrings.elementAt( i + 1 ), 103 ( String ) weatherStrings.elementAt( i + 2 ) ) ); 104 } 105 106 return list; 107 } 108 109 // execute WeatherServiceClient 110 publicstaticvoid main( String args[] ) 111 { 112 WeatherServiceClient client = null; 113 114 // if no server IP address or host name specified, 115 // use "localhost"; otherwise use specified host 116 if ( args.length == 0 ) 117 client = new WeatherServiceClient( "localhost" ); 118 else 119 client = new WeatherServiceClient( args[ 0 ] ); 120 121 // configure and display application window 122 client.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ); 123 client.pack(); 124 client.setResizable( false ); 125 client.setVisible( true ); 126 } 127 } Fig. 29.6 SOAP implementation of class Weather-ServiceClient (part 4).

  18. 29.3 SOAP Weather Service (cont.) Fig. 29.7 Apache SOAP Admin page.

  19. 29.3 SOAP Weather Service (cont.) Fig. 29.8 Apache SOAP Service Deployment Descriptor Template.

  20. 29.3 SOAP Weather Service (cont.) Fig. 29.9 SOAP WeatherService Client.

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