Chapter 29: Introduction to Web Services and SOAP

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Chapter 29: Introduction to Web Services and SOAP

Outline

29.1 Introduction

29.2 Simple Object Access Protocol (SOAP) 29.3 SOAP Weather Service

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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

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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

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 2002 Prentice Hall.

Outline

Fig. 29.1 Class SimpleService.

Line 4 Lines 6-12

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 }

Class SimpleService resides on a server

Method returns a String when invoked; this method is made

available to remote clients

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29.2 Simple Object Access Protocol (SOAP) (cont.)

Fig. 29.2 SOAP package administration tool.

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29.2 Simple Object Access Protocol (SOAP) (cont.)

Fig. 29.3 Description of deployed service.

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Outline

Fig. 29.4 Client making a SOAP request (part 1).

Lines 10-11 Line 13 Line 17 Lines 27-28 Lines 31-33

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

Client for the RPC

SOAP-implementation APIs

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

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Outline

Lines 40-44 Line 48 Lines 51-57 Lines 60-63

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

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

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Outline

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() );

78 } 79 } 80 }

java GetMessage Welcome to SOAP!

Here is your message: Thanks!

java GetMessage "my message”

Welcome to SOAP!

Here is your message: my message

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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

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Outline

Fig. 29.5 SOAP implementation of class Weather- Service (part 1).

Line 11

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 public class WeatherService {

12

13 private Vector weatherInformation; // WeatherBean objects 14

15 // get weather information from NWS 16 private void 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

Class WeatherService provides method getWeatherInformation that class WeatherServiceClient

calls through SOAP RPC

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Outline

Lines 66-71

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 ) );

Add Strings parsed from Traveler’s Forecast Web

page to Vector

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Outline

Lines 95-100

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();

85 } 86

87 // process other exceptions 88 catch( Exception exception ) { 89 exception.printStackTrace();

91 } 92 } 93

94 // implementation for WeatherService interface method 95 public Vector getWeatherInformation()

96 {

97 updateWeatherConditions();

98

99 return weatherInformation;

100 } 101 }

Method getWeatherInformation is made available to remote clients

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Outline

Fig. 29.6 SOAP implementation of class Weather- ServiceClient (part 1).

Lines 31-32

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 public class 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

Set SOAP service’s URL

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Outline

Lines 35-37 Line 46 Lines 49-55

Lines 58-65

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

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

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Outline

Line 95

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(); Covert Vector of Strings to List of WeatherBeans

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Outline

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 public static void 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 }

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29.3 SOAP Weather Service (cont.)

Fig. 29.7 Apache SOAP Admin page.

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29.3 SOAP Weather Service (cont.)

Fig. 29.8 Apache SOAP Service Deployment Descriptor Template.

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29.3 SOAP Weather Service (cont.)

Fig. 29.9 SOAP WeatherService Client.