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Oracle® Application Server Containers for J2EE JSP Tag Libraries and Utilities Reference 10g Release 2 (10.1.2) B14016-02 |
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# 11 Web Services Tags

Oracle furnishes a tag library with OC4J that enables developers to create JSP pages for use as client programs for Web services. This chapter describes the tag library and consists of the following sections:

- Overview of Web Services

- OC4J Web Services Tags

This chapter is written with the assumption that you are already familiar with Web services, Simple Object Access Protocol (SOAP), and the Web Services Description Language (WSDL); however, some overview is provided here. There are also references to additional documents, including related specifications from the World Wide Web Consortium (W3C).

The OC4J Web services tag library is based on Oracle Application Server Web Services. See the Oracle Application Server Web Services Developer's Guide for information.

## Overview of Web Services

The following sections provide a quick overview of Web services concepts:

- General Web Services Overview

- Overview of SOAP and Related Features

- Overview of Web Services Description Language Key Elements

- Overview of Web Service Messages and XML Schema Definitions

- Web Service Example

### General Web Services Overview

Web services are sets of procedures, or actions, that can be invoked by a client over the Internet, regardless of the computing platform. Web services consist of loosely coupled components over a distributed computing environment following a widely adopted set of standards such as SOAP, WSDL, and UDDI (all discussed later in this chapter). As an example, there might be a "World Cup Soccer" service that consists of actions to get scores, schedules, and standings.

A Web service must have the following features:

- It must be able to describe itself, such as its functionality and its input and output attributes. A Web service describes itself through an XML-style WSDL document. See "Overview of Web Services Description Language Key Elements".

- It mu st make itself generally available so that client applications can access it. The standard way to do this is to be listed in a Universal Description, Discovery, and Integration (UDDI) directory. Public UDDI directories are available to aggregate groups of businesses or users (or perhaps to anyone on the Internet), while private UDDI directories are available only within a particular business or group.

- A client application must be able to invoke it through a standard protocol once the application has found and examined it. A leading protocol for Web services is Simple Object Access Protocol (SOAP). With SOAP, the Web service is behind a SOAP server at the server end and the client application goes through a SOAP server at the client end. Data exchanges are "SOAP-enveloped" and can gain access through firewalls. This SOAP exchange is conceptually similar to a Remote Method Invocation (RMI) exchange, except that RMI exchanges cannot go through firewalls. See "Overview of SOAP and Related Features" below for a brief overview of SOAP.

- Once invoked, it must return a response to provide requested results to the client application. This is performed through the same standard protocol, such as SOAP.

For more information about Web services, particularly OracleAS Web Services, you can refer to the Oracle Application Server Web Services Developer's Guide.

For related specifications, refer to the following Web sites for the W3C SOAP specification, W3C WS DL specification, and UD DI specification, respectively:

    http://www.w3.org/TR/SOAP

    http://www.w3.org/TR/wsdl

    http://www.uddi.org/specification.html

### Over view of SOAP and Related Features

This section offers a brief overview of SOAP. See the W3C Simple Object Access Protocol (SOAP) 1.1 specification for details.

SOAP is a lightweight, X ML-based protocol for exchanging typed and structured data over the Internet or other distributed environments. Among other features, SOAP supports remote procedure call (RPC) and message-oriented data exchanges.

In a message-oriented imple mentation, data is exchanged through a modular packaging and encoding model. A message is a WSDL component that specifies input data parts and output data parts associated with an operation. See "Overview of Web Service Messages and XML Schema Definitions" for more information.

RPC is an alternative to sockets, with the communication interface being at the level of procedure calls. It is as though you are calling a local procedure, but arguments of the call are actually packaged and sent to a remote target. The RPC mechanism uses a request/response methodology, where an end-point receives a procedure-oriented message and sends back a corresponding response.

Using SOAP with RPC is independent of the protocol binding. Where HTTP is the protocol binding, HTTP requests correspond to RPC calls, and HTTP responses correspond to RPC responses.

Key aspects of SOAP include the following.

- SOAP envelope construct: The envelope encloses a SOAP header and SOAP body and indicates what is in a message, whether it is required, and who should process it.

- SOAP encoding rules: Encoding rules define serialization mechanisms for the exchange of instances of the datatypes used in an application.

- SOAP RPC representation: The RPC representation specifies a convention for representing RPC calls and responses.

### Overvie w of Web Services Description Language Key Elements

A Web service is described using the XML-based Web Services Description Language in a WSDL (`.wsdl`) document.

Following are some key WSDL terms.

- Ope ration: An operation is a particular action performed by a service, such as any of the "get scores", "get schedules", and "get standings" examples for a World Cup service.

- Mes sage: A message is an abstract definition that specifies the data that is being input and output for an operation.

- Po rt type: A port type is an abstract definition of the operations supported by a service.

- Bin ding: A binding is a protocol and data format specification for one or more operations supported by a service. A binding mechanism maps the generic or abstract definition of a Web service to a concrete implementation, including data encoding, message protocol, and communication protocol.

- P ort: A port is a single end-point, a combination of a binding and a network address. Essentially, a port is the concrete manifestation of the capabilities described by a port type. In a SOAP-based implementation, a port is a SOAP location.

  To be more precise than previously, a Web service is really a collection of related ports, or end-points, not just a collection of abstract actions or operations.

The WSDL specification outlines the general structure of a WSDL document, which includes the following key elements. Refer to the W3C Web Services Description Language (WSDL) 1.1 specification for complete information.

- A `<types>` element , through one or more `<schema>` subelements, contains descriptions of the data that is exchanged in messages used by the operations of the service.

- A `<message>` element provides an abstract definition of data being sent as input or output for an operation.

- A `<portType>` element, through one or more `<operation>` subelements, contains abstract definitions of the operations of the Web service. An `<operation>` element specifies the message that is used for input and the message that is used for output for the operation.

- A `<binding>` element, also through `<operation>` subelements, binds each operation to the particular protocol and data formats to be used.

- A `<service>` element defines the ports, or end-points, of the Web service. Within the `<service>` element is one or more `<port>` subelements, where each `<port>` element ties a binding to an address to define the end-point.

### Overv iew of Web Service Messages and XML Schema Definitions

Messages define parameters used by the operations, or methods, of a Web service. A message is a typed definition of the data being communicated, consisting of one or more parts. Each part corresponds to a logical entity, such as a "Purchase Order" part and an "Invoice" part. For each part, there are type specifications for the associated data items.

In a SOAP-based implementation, such as for OracleAS Web Services, the datatypes used by a message are defined through the XML Schema Definition (XSD) language, which supports predefined simple types as well as user-defined complex types.

With an implementation that uses XSD, the syntax for defining a message is as follows:

       <message name="nmtoken">
          <part name="nmtoken" [type="qname"] [element="qname"] />
       </message>

In this syntax, the `element` attribute refers to where an XSD complex type is defined using XSD syntax, the `type` attribute indicates an XSD simple type, "`nmtoken`" indicates a standard XML name token, and "`qname`" indicates a standard XML qualified name. There can be zero or more messages, and zero or more parts for each message.

For a SOAP encoding style of `encoded`, only simple types are allowed, so the `element` attribute is not used. For an encoding style of `literal`, you can have simple types or complex types, so a `<part>` element can use either the `type` attribute or the `element` attribute, but not both.

Here is an example of a message definition, from "Example: WSDL Definition", which follows shortly:

       <message name="GetLastTradePriceInput">
          <part name="body" element="xsd1:TradePriceRequest"/>
       </message>

`GetLastTradePriceInput` is the name of the message, which is an input message (as the name implies). In this case, the `element` attribute refers to a namespace where a complex type, `TradePriceRequest`, is defined. Here is an example of such a definition (also part of "Example: WSDL Definition" below):

       <element name="TradePriceRequest">
          <complexType>
             <all>
                 <element name="tickerSymbol" type="string"/>
                 <element name="companyName" type="string"/>
             </all>
          </complexType>
       </element>

An XML schema primer is available from W3C at the following location:

    http://www.w3.org/TR/xmlschema-0/

### Web Service Example

This example shows the WSDL definition of a Web service, illustrating the input and output messages embedded in an HTTP request and HTTP response, respectively.

#### Exam ple: WSDL Definition

The W3C Web Services Description Language (WSDL) 1.1 specification provides the following example of a WSDL document that defines a stock quote service taking a ticker symbol as input and returns the current stock price as output. Note this uses a SOAP encoding style of `literal`, so complex types are allowed (and used).

    <?xml version="1.0"?>
    <definitions name="StockQuote"

    targetNamespace="http://example.com/stockquote.wsdl"
              xmlns:tns="http://example.com/stockquote.wsdl"
              xmlns:xsd1="http://example.com/stockquote.xsd"
              xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
              xmlns="http://schemas.xmlsoap.org/wsdl/">

       <types>
          <schema targetNamespace="http://example.com/stockquote.xsd"
                  xmlns="http://www.w3.org/2000/10/XMLSchema">
             <element name="TradePriceRequest">
                <complexType>
                   <all>
                      <element name="tickerSymbol" type="string"/>
                   </all>
                </complexType>
             </element>
             <element name="TradePrice">
                <complexType>
                   <all>
                      <element name="price" type="float"/>
                   </all>
                </complexType>
             </element>
          </schema>
       </types>

       <message name="GetLastTradePriceInput">
          <part name="body" element="xsd1:TradePriceRequest"/>
       </message>

       <message name="GetLastTradePriceOutput">
          <part name="body" element="xsd1:TradePrice"/>
       </message>

       <portType name="StockQuotePortType">
          <operation name="GetLastTradePrice">
             <input message="tns:GetLastTradePriceInput"/>
             <output message="tns:GetLastTradePriceOutput"/>
          </operation>
       </portType>

       <binding name="StockQuoteSoapBinding" type="tns:StockQuotePortType">
          <soap:binding style="document"
                        transport="http://schemas.xmlsoap.org/soap/http"/>
          <operation name="GetLastTradePrice">
             <soap:operation soapAction="http://example.com/GetLastTradePrice"/>
                <input>
                   <soap:body use="literal"/>
                </input>
                <output>
                   <soap:body use="literal"/>
                </output>
          </operation>
       </binding>

       <service name="StockQuoteService">
          <documentation>My first service</documentation>
             <port name="StockQuotePort" binding="tns:StockQuoteBinding">
                <soap:address location="http://example.com/stockquote"/>
              </port>
       </service>

    </definitions>

This WSDL definition first specifies the `GetLastTradePriceInput` and `GetLastTradePriceOutput` input and output messages, then ties them to the operation `GetLastTradePrice`, then defines a binding and a port for that operation.

Notes: This example has all aspects of the Web service definition, including the XML schema definitions for data exchanges, in the same document. Alternatively, `stockquote.xsd`, for example, could be a separate XSD document instead of a namespace within this document. The W3C WSDL specification illustrates this. Be aware, however, that the OC4J Web services tag library does not support WSDL documents that use `<import>` elements to import other WSDL documents. The example uses a document-style binding. The OC4J 10.1.2 implementation of the Web services tag library supports RPC-style and document-style bindings. In the document-style case, the output response object is an XML document of type `XMLElement`. In the RPC-style case, the output object might be of any type.

#### Example: SOAP Messages Embedded in HTTP Request and Response

Corresponding to the Web service defined in the preceding example, this section shows what the messages would look like, with the soap-enveloped input message embedded in an HTTP request, and the soap-enveloped output message embedded in an HTTP response. These examples are also from the W3C Web Services Description Language (WSDL) 1.1 specification.

Here is a request:

    POST /StockQuote HTTP/1.1
    Host: www.stockquoteserver.com
    Content-Type: text/xml; charset="utf-8"
    Content-Length: nnnn
    SOAPAction: "SOAP_URI"

       <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
          <soapenv:Body>
             <m:GetLastTradePrice xmlns:m="xmlns_URI">
                <m:tickerSymbol>DIS</m:tickerSymbol>
             </m:GetLastTradePrice>
          </soapenv:Body>
       </soapenv:Envelope>

In this example, `xmlns_URI` is a URI value used to identify the namespace where the `GetLastTradePrice` operation and its messages are defined, such as the WSDL document in the preceding "Example: WSDL Definition". This is also where `tickerSymbol` is defined. The request is for a stock quote for Walt Disney Company. `SOAP_URI` is the URI for the SOAP action HTTP header for the HTTP binding of SOAP.

And here is the response:

    HTTP/1.1 200 OK
    Content-Type: text/xml; charset="utf-8"
    Content-Length: nnnn

       <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
          <soapenv:Body>
             <m:GetLastTradePriceResponse xmlns:m="Some_URI">
                <m:price>34.5</m:price>
             </m:GetLastTradePriceResponse>
          </soapenv:Body>
       </soapenv:Envelope>

By convention, the response for an operation `Xxxx` is called `Xxxx` `Response`. `Some_URI` is a URI value used to identify the namespace where the `GetLastTradePriceResponse` operation is defined.

## OC4J Web Services Tags

The following sections provide an overview and details of the Web services tag library, as well as an overview of OracleAS Web Services, upon which the tag library implementation is based.

- Overview of OracleAS Web Services and the Tag Library Implementation

- Overview of Functionality of Web Services Tags

- Web Services Tag Descriptions

- Web Services Tag Examples

### Overv iew of OracleAS Web Services and the Tag Library Implementation

The Web services tag library provided with OC4J enables developers to conveniently create JSP pages for Web service client applications. The implementation uses a SOAP-based mechanism. A client application would access the WSDL document, then use the WSDL information to access the operations of a Web service.

The tag library also uses the Oracle implementation of the dynamic invocation API, described in the Oracle Application Server Web Services Developer's Guide. When a client application acquires a WSDL document at runtime, the dynamic invocation API is the vehicle for invoking any SOAP operation described in the WSDL document. The tag handler uses the API when sending a SOAP request that invokes a Web service and when handling the SOAP response.

The Oracle dynamic invocation API consists of classes and interfaces in the `oracle.j2ee.ws.client` and `oracle.j2ee.ws.client.wsdl` packages.

The `oracle.j2ee.ws.client` package includes the following.

- `WebServiceProxyFactory`: Given a WSDL document (through a Java input stream that contains the document or through the URL of the document), a `WebServiceProxyFactory` instance can use the name of a service and the name of one of its ports, as specified in the WSDL document, to create a `WebServiceProxy` instance (an instance of a class that implements the `WebServiceProxy` interface).

- `WebServiceProxy`: Use this interface in representing a service defined in a WSDL document. Each `WebServiceProxy` instance is based on the location of the WSDL document and, optionally, on additional qualifiers that identify which service and port should be used. A `WebServiceProxy` class exposes methods to determine the WSDL port type, including the syntax and signatures of all operations exposed by the WSDL document, and to invoke the defined operations.

- `WebServiceMethod`: Use this interface in invoking a Web service method, or operation.

The `oracle.j2ee.ws.client.wsdl` package includes the following.

- `Operation`: This interface represents a WSDL operation.

- `Message`: This interface represents a message used in the input or output of an operation.

- `Part`: This interface represents a message part.

- `Input`: This interface represents an input message.

- `Output`: This interface represents an output message.

  Note: The dynamic invocation API is packaged in `dsv2.jar` in the `ORACLE_HOME``/lib` directory. Also note that the SOAP implementation requires `soap.jar` in the `ORACLE_HOME``/soap` directory.

### Overview of Functionality of Web Services Tags

This section provides an overview of the OC4J Web services tag library and its functionality. The tag library includes support for the following:

- Binding to a Web service

- Using a Web service operation through SOAP requests and SOAP responses

- Defining input and output message parts

- Mapping SOAP/XML datatypes to Java types

- Setting custom properties for use by the client application

The tag library supports invoking operations defined in WSDL documents that use the W3C XML schema version whose namespace is the following:

    http://www.w3.org/2001/XMLSchema

The Web services tag library includes the `webservice` tag, optionally with nested `map` and `property` tags, and the `invoke` tag, optionally with nested `part` tags. They are used as follows.

- `webservice`: Use this tag to create a Web service proxy. The tag requires the URL of a WSDL document and then uses one of the following combinations:

  - A binding and SOAP location, useful for a WSDL document identified in a UDDI registry

  - A service name and port, provided through tag attributes or through the first service and its first port from the WSDL document

- `map`: The Web service proxy uses this tag, if specified, to add an entry to the SOAP mapping registry, which is a registry that maps local SOAP/XML types to Java types. Any number of `map` tags can be nested within a `webservice` tag, one tag for each desired type mapping.

- `property`: Optionally, use this tag to define any of several supported custom properties for use by the Web service client application. Each `property` tag must be nested within the `webservice` tag; the property will have the same scope as the parent Web service.

- `invoke`: Use this tag to invoke an operation of the Web service. An `invoke` tag accesses a Web service proxy either by being nested within a `webservice` tag, or through a scripting variable.

- `part`: If an operation has input message parts, use `part` tags, nested within an `invoke` tag, to define the message parts. Use one `part` tag for each part.

  Notes: The tag library does not support the use of `<import>` elements within WSDL documents to import other WSDL documents. Custom bindings, including custom HTTP bindings or custom MIME bindings, are not supported. Because the OC4J Web services tag library implementation is based on the OracleAS Web Services implementation, any additional limitations of OracleAS Web Services also apply to the tag library.

### Web Services Tag Descriptions

The following sections supply detailed descriptions of the OC4J Web services tags, a standards-compliant JavaServer Pages tag library implementation, including syntax documentation:

- Web Services webservice Tag

- Web Services map Tag

- Web Services property Tag

- Web Services invoke Tag

- Web Services part Tag

Note the following requirements for the Web services tag library:

- The Web services tag library is included in the `ojsputil.jar` file. This file is provided with OC4J, in the "well-known" tag library directory. Verify that this file is installed and in your classpath.

- The ta g library descriptor, `wstaglib.tld`, must be available to the application, and any JSP page using the library must have an appropriate `taglib` directive. In an Oracle Application Server installation, the TLD is in `ojsputil.jar`. The `uri` value for `wstaglib.tld` is the following:

      http://xmlns.oracle.com/j2ee/jsp/tld/ojsp/wstaglib.tld

You can refer to the Oracle Application Server Containers for J2EE Support for JavaServer Pages Developer's Guide for information about `taglib` directives, the well-known tag library directory, TLD files, and the meaning of `uri` values.

For an example that uses the tags described in this section, see "Web Services Tag Examples".

Notes: The prefix "ws:" is used in the tag syntax here. This is by convention, but is not required. You can specify any desired prefix in the `taglib` directive. See "Tag Syntax Symbology and Notes" for general information about tag syntax conventions in this manual.

#### Web Services w ebservice Tag

Use this tag to create a Web service proxy, an instance of a class that implements the `oracle.j2ee.ws.client.WebServiceProxy` interface. The tag requires the URL of a WSDL document and uses a binding and SOAP location or a service name and port, as follows:

1. First, if tag attributes provide a binding and SOAP location, the tag handler uses them in creating the proxy. Tag attributes for service name and port are ignored in this case.

2. If no binding and SOAP location are provided, the tag handler uses a service name and port, as follows:

   1. If a service name and port are provided through tag attributes, then the tag handler uses them in creating the proxy.

   2. If no service name and port are provided, the tag handler uses the first service in the WSDL document and the first port listed for that service.

Using a binding and SOAP location is particularly useful for a Web service whose WSDL document is accessed through a UDDI registry. In that case, the binding and location can be determined through UDDI queries and supplied to the tag through request-time expressions.

After the Web service proxy is created, it will use any nested `map` tags to add entries to the SOAP mapping registry. See the next section, "Web Services map Tag".

##### Syntax

    <ws:webservice wsdlUrl = "WSDL_URL_of_Web_service"
                 [ id = "variable_name_for_Web_service_proxy" ]
                 [ scope = "page" | "request" | "session" | "application" ]
                 [ binding = "SOAP_binding_information" ]
                 [ soapLocation = "SOAP_endpoint_URL" ]
                 [ service = "service_name_in_WSDL" ]
                 [ port = "port_name_for_service" ] >

    ...body / nested tags...

    </ws:webservice>

Note: The `scope` attribute cannot take request-time expressions.

##### Attributes

- `wsdlUrl` (required): Use this attribute to specify a URL where the WSDL for the desired Web service can be accessed.

- `id`: If the Web service is to be accessed by an `invoke` tag that is not nested within the `webservice` tag, use the `id` attribute to specify the name for a `WebServiceProxy` scripting variable so that the variable can be referenced by the `invoke` tag. The specified name must be a valid Java identifier. When you use the `id` attribute, the specified variable will be declared automatically with scope `AT_END` (available from the `webservice` end-tag to the end of the JSP page).

- `scope`: Optionally, specify the scope of the `webservice` tag. The default setting is "`page`".

- `binding`: In scenario #1 above, use the `binding` attribute to specify the SOAP binding information for a SOAP location (end-point URL) that you specify through the `soapLocation` attribute. You must use these attributes together. The binding information is as defined in the WSDL document, specifying concrete protocol and data format specifications for the operations and messages defined by a particular port type.

- `soapLocation`: In scenario #1 above, use `soapLocation` to specify a SOAP location (end-point URL) as defined in the WSDL document, for which the binding information specified through the `binding` attribute applies. You must use these attributes together.

- `service`: In scenario #2a above, use the `service` attribute to specify the name of a service defined in the WSDL document. You must use this attribute with the `port` attribute, but both are ignored if you use `binding` and `soapLocation`.

- `port`: In scenario #2a above, use the `port` attribute to specify a port for the service that is specified through the `service` attribute. You must use these attributes together. The Web service proxy will use the specified port. The port address will be as specified in the corresponding `<service>` element in the WSDL document. The `service` and `port` attributes are ignored if you use `binding` and `soapLocation`.

#### Web Ser vices map Tag

For interoperability, a mapping mechanism is necessary to map WSDL-defined SOAP/XML datatypes to the Java types used in JSP pages of a Java client application. This is possible through the OracleAS Web Services SOAP mapping registry.

You can have any number of `map` tags nested within a `webservice` tag, to have the Web service proxy add entries to the registry. Use one `map` tag for each desired type mapping.

The registry is an instance of the `XMLJavaMappingRegistry` class of the `org.apache.soap.util.xml` package. A `WebServiceProxy` instance has a `getXMLMappingRegistry()` method to access the registry.

The `map` tag includes attributes to specify the encoding style, serialization utility (class name), deserialization utility (class name), and namespace URI to facilitate the type mapping. The Web services tag library supports custom classes for serialization and deserialization, if you want to create your own.

Important: When using a `map` tag, you must nest it within a `webservice` tag.

##### Syntax

    <ws:map localName = "local_name_of_SOAPXML_type"
            namespaceUri = "URI_of_namespace_for_SOAPXML_type"
            javaType = "Java_type_to_map"
            encodingStyle = "URL_of_SOAP_encoding_style"
            java2xmlClassName = "Java_to_XML_serializer"
            xml2javaClassName = "XML_to_Java_deserializer" />

##### Attributes

- `localName` (required): Specify the local name of the SOAP/XML datatype, such as `SOAPStruct`, for example.

- `namespaceUri` (required): Specify a valid URI for the namespace of the SOAP/XML datatype. The following is an example:

      http://soapinterop.org/xsd

- `javaType` (required): Specify the Java type which you want to map to the SOAP/XML type. The types must be legally mappable.

- `encodingStyle` (required): Specify a valid URI for a SOAP encoding style. The following is an example:

      http://schemas.xmlsoap.org/soap/encoding

- `java2xmlClassName` (required): Specify the class name with the functionality for serializing the data for Java-to-XML conversion. This can be a custom class. The following is an example:

      org.apache.soap.encoding.soapenc.BeanSerializer

- `xml2javaClassName` (required): Specify the class name with the functionality for deserializing the data for XML-to-Java conversion. This can be a custom class. The following is an example:

      org.apache.soap.encoding.soapenc.BeanSerializer

#### Web Services pro perty Tag

You can optionally use this tag to specify a name/value pair that defines any of several supported custom properties for use by the Web service client application. For example, you could use `property` tags to specify an HTTP proxy host and proxy port if a proxy is required for access through a network firewall. The following properties are supported:

- `http.proxyHost`: Use this property to specify the host name of an HTTP proxy server.

- `http.proxyPort`: Use this property to specify a port number of an HTTP proxy server.

- `javax.net.ssl.KeyStore`: Use this property to specify the full path of an Oracle security wallet file.

  Important: When using a `property` tag, you must nest it within a `webservice` tag. The property will have the same scope as the parent Web service.

##### Syntax

    <ws:property name="http.proxyHost" | "http.proxyPort" | "javax.net.ssl.KeyStore"
                 value = "property_value" />

##### Attributes

- `property` (required): Specify the property you want to set; it must be one of the supported properties listed in the tag syntax.

- `value` (required): Specify the desired value of the property—a host name, port number, or full path to an Oracle wallet file.

#### Web Services inv oke Tag

Use this tag to invoke an operation of the Web service. The tag handler will call the remote Web service operation by passing an input message in a SOAP request, then will wait for the SOAP response. You must specify the operation, as well as an object ID for the object that will contain the returned response. The tag handler uses the operation name to find the operation in the WSDL document.

The `invoke` tag gains access to a Web service proxy in one of two ways:

- The `invoke` tag is nested within the `webservice` tag that establishes the proxy.

- The `invoke` tag uses its `webservice` attribute to access a `WebProxyService` scripting variable created through a `webservice` tag `id` attribute.

In a situation where there are overloaded operations (two operations of the same name using different I/O messages), the `invoke` tag has attributes to specify the input and output message names for the desired operation. In this case, for RPC-style bindings, the specified input and output message names are used to form the RPC signature of the operation. Otherwise, the RPC signature is the default according to the WSDL document.

If the output message has multiple parts, then the returned result is an array of message parts (all within a single SOAP response).

The `invoke` tag can act as an XML producer, supporting explicit passing of an XML output object through the `toXMLObjName` attribute. This is useful if the `invoke` tag is nested inside other kinds of tags such as Web Object Cache tags or the XML `transform` tag. Also note that an XML output object can be written to the `JspWriter` object of the JSP page for output directly to the user's browser. This is enabled through the `xmlToWriter` attribute.

Notes: Waiting for the SOAP response is a blocking function. The scope of the output result object, identified by the `id` attribute, is the same as the scope of the proxy object defined in the `webservice` tag for the Web service. For an `invoke` tag nested within a `webservice` tag, this scope is from the `webservice` start-tag to the `webservice` end-tag. However, the `id` object can still be accessed outside the `webservice` tag through use of the `findAttribute()` method of the JSP page context object.

##### Syntax

    <ws:invoke id = "variable_name_for_output_result"
               operation = "operation_to_invoke"
             [ webservice = "variable_name_of_Web_service_proxy" ]
             [ inputMsgName = "name_of_input_message" ]
             [ outputMsgName = "name_of_output_message" ]
             [ xmlToWriter = "true" | "false" ]
             [ toXMLObjName = "objectname" ] >

    ...body / nested tags...

    </ws:invoke>

##### Attributes

- `id` (required): Specify a scripting variable name for the output result object. The specified name must be a valid Java identifier. See the note preceding the tag syntax above for information about the scope of the `id` object.

- `operation` (required): Specify an operation to be executed (an operation from the WSDL document).

- `webservice`: Use this attribute if you want to specify the name of a `WebServiceProxy` scripting variable corresponding to the service to invoke. This is not necessary if the `invoke` tag is nested inside the `webservice` tag that accesses the desired service.

- `inputMsgName`: Optionally specify the input message name—the name of a `wsdl:input` tag in the WSDL document—for the operation. This is only necessary if there are overloaded operations (operations with the same name that use different message names).

- `outputMsgName`: Optionally specify the output message name—the name of a `wsdl:output` tag in the WSDL document—for the operation. This is necessary only if there are overloaded operations (operations with the same name that use different message names).

- `xmlToWriter`: For a document-style Web service, and if the output is an XML object, set this attribute to "`true`" if you want to output the XML to the `JspWriter` output object of the JSP page. The default setting is "`false`".

- `toXMLObjName`: For a document-style Web service, and if you want to explicitly pass the output in an XML object, use this attribute to specify the name of the object.

#### Web Services p art Tag

Use this tag, nested within an `invoke` tag, if the operation being performed requires input message part values, using one `part` tag for each input part.

How to specify the part value might depend on whether you are using an RPC-style or document-style Web service. For RPC-style, you must use the `value` attribute. For document-style, you have the option of passing the value through an XML request element in the tag body.

Note: If you use both a tag body and the `value` attribute, the tag body is ignored.

##### Syntax

    <ws:part name = "part_name"
           [ value = "part_value" ] >

    ...optional body, with request element, for document-style...

    </ws:part>

##### Attributes

- `name` (required): Specify the name of the input part (a valid Java identifier).

- `value`: Specify the value of the input part. This is required for an RPC-style Web service. For a document-style Web service, you can use the tag body instead.

### Web Servi ces Tag Examples

This section provides a template for use of the Web services tag library, a sample JSP page to invoke an RPC-style Web service, and a sample page to invoke a document-style Web service.

#### Web Services Example: Usage Template

    <HTML>
    <HEAD>
    <TITLE>Title</TITLE>
    </HEAD>
    <BODY>
    <H2>This is sample HTML text.</H2>
    <%@ taglib uri="http://xmlns.oracle.com/j2ee/jsp/tld/ojsp/wstaglibrary.tld"
               prefix="ws" %>
    <ws:webservice id="myws"
                   wsdlUrl="wsdlurl"
                   {
                      binding="" soapLocation="" | service="" port=""
                   }
                   {
                      scope="page | request | session | application"
                   }
                    >
       <ws:property name="property" value="string"/>

       <ws:map encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
               localname="SOAPStruct"
               namespaceUri="http://soapinterop.org/xsd"
               javaType="MySoapStructBean"
               java2xmlClassName="org.apache.soap.encoding.soapenc.BeanSerializer"
               xml2javaClassName="org.apache.soap.encoding.soapenc.BeanSerializer"
        />

    </ws:webservice>

    <ws:invoke id="result" webservice="myws" operation="add" inputMsgName=""
               outputMsgName="">
       <ws:part name="part_name" value="{string | <%= expression %>}"/>
    </ws:invoke>

    <% =result %>
    </BODY>
    </HTML>

#### Web Services Example: Sample JSP Page for RPC-Style Web Service

    <%@ page contentType="text/html"%>
    <%@ taglib uri="http://xmlns.oracle.com/j2ee/jsp/tld/ojsp/wstaglib.tld"
               prefix="ws" %>
    <HTML>
    <HEAD>
    <META HTTP-EQUIV="Content-Type" CONTENT="text/html; ">
    </HEAD>
    <BODY>
    <%
     String itemID = request.getParameter("itemID");
    %>
    <ws:webservice id="ebay"
        wsdlUrl="http://www.xmethods.net/sd/2001/EBayWatcherService.wsdl"
        binding="eBayWatcherBinding"
        soapLocation="http://services.xmethods.net:80/soap/servlet/rpcrouter"
        scope="page">
      <ws:property name="http.proxyHost" value="www-proxy.us.oracle.com"/>
      <ws:property name="http.proxyPort" value="80"/>
    </ws:webservice>
    <ws:invoke id="price" webservice="ebay" operation="getCurrentPrice">
      <ws:part name="auction_id" value="<%=itemID%>"/>
    </ws:invoke>
    <B>
    Action price for eBay Item # <%=itemID%> is :
    </B>
    <P>
    $<%= price%>
    @
    <%= new java.util.Date()%>
    </P>
    </BODY>
    </HTML>

#### Web Services Example: Sample JSP Page for Document-Style Web Service

    <%@ page contentType="text/xml;"%>
    <%@ page  import= oracle.xml.parser.v2.XMLElement;"%>
    <%@ taglib uri="http://xmlns.oracle.com/j2ee/jsp/tld/ojsp/wstaglib.tld"
               prefix="ws" %>
    <%@ taglib uri="http://xmlns.oracle.com/j2ee/jsp/tld/ojsp/xml.tld"
               prefix="xml" %>
    <ws:webservice id="bookService"
            wsdlUrl="http://hosting.msugs.ch/cheeso9/books/books.asmx?WSDL"
            binding="LookyBookServiceSoap"
            soapLocation ="http://hosting.msugs.ch/cheeso9/books/books.asmx"
            scope="session">
    </ws:webservice>
    <ws:invoke id="bookResult"
            operation="GetInfo"
            webservice="bookService">
        <ws:part name="parameters">
            <GetInfo xmlns="http://dinoch.dyndns.org/webservices/">
              <ISBN>SomeISBNNumber</ISBN>
            </GetInfo>
        </ws:part>
    </ws:invoke>
    <%
        XMLNode resultNode = (XMLNode) bookResult;
        resultNode.Error! Bookmark not defined.(new java.io.PrintWriter(out));
    %>
    </BODY>
    </HTML>