The SOAP Message Object (Sun Java System Message Queue 4.3 Developer's Guide for Java Clients)

Sun Java System Message Queue 4.3 Developer's Guide for Java Clients

The SOAP Message Object

A SOAP Message Object is a tree of objects as shown in Figure 5–5. The classes or interfaces from which these objects are derived are all defined in the javax.xml.soap package.

Figure 5–5 SOAP Message Object

Diagram showing hierarchy of objects that make up a SOAP
message object. Long description follows figure.

As shown in the figure, the SOAPMessage object is a collection of objects divided in two parts: a SOAP part and an attachment part. The main thing to remember is that the attachment part can contain non-xml data.

The SOAP part of the message contains an envelope that contains a body (which can contain data or fault information) and an optional header. When you use SAAJ to create a SOAP message, the SOAP part, envelope, and body are created for you: you need only create the body elements. To do that you need to get to the parent of the body element, the SOAP body.

In order to reach any object in the SOAPMessage tree, you must traverse the tree starting from the root, as shown in the following lines of code. For example, assuming the SOAPMessage is MyMsg, here are the calls you would have to make in order to get the SOAP body:

SOAPPart MyPart = MyMsg.getSOAPPart();
SOAPEnvelope MyEnv = MyPart.getEnvelope();
SOAPBody MyBody = envelope.getBody();

At this point, you can create a name for a body element (as described in Namespaces) and add the body element to the SOAPMessage.

For example, the following code line creates a name (a representation of an XML tag) for a body element:

Name bodyName = envelope.createName("Temperature");

The next code line adds the body element to the body:

SOAPBodyElement myTemp = MyBody.addBodyElement(bodyName);

Finally, this code line defines some data for the body element bodyName :

myTemp.addTextNode("98.6");

Inherited Methods

The elements of a SOAP message form a tree. Each node in that tree implements the Node interface and, starting at the envelope level, each node implements the SOAPElement interface as well. The resulting shared methods are described in Table 5–1.

Table 5–1 Inherited Methods

Inherited From

Method Name

Purpose

SOAPElemen

addAttribute(Name, String)

Add an attribute with the specified Name object and string value

addChildElement(Name)
addChildElement(String, String)
addChildElement
    (String, String, String)

Create a new SOAPElement object, initialized with the given Name object, and add the new element

(Use the Envelope.createName method to create a Name object)

addNameSpaceDeclaration 
   (String, String)

Add a namespace declaration with the specified prefix and URI

addTextnode(String)

Create a new Text object initialized with the given String and add it to this SOAPElement object

getAllAttributes()

Return an iterator over all the attribute names in this object

getAttributeValue(Name)

Return the value of the specified attribute

getChildElements()

Return an iterator over all the immediate content of this element

getChildElements(Name)

Return an iterator over all the child elements with the specified name

getElementName()

Return the name of this object

getEncodingStyle()

Return the encoding style for this object

getNameSpacePrefixes()

Return an iterator of namespace prefixes

getNamespaceURI(String)

Return the URI of the namespace with the given prefix

removeAttribute(Name)

Remove the specified attribute

removeNamespaceDeclaration
(String)

Remove the namespace declaration that corresponds to the specified prefix

setEncodingStyle(String)

Set the encoding style for this object to that specified by String

Node

detachNode()

Remove this Node object from the tree

getParentElement()

Return the parent element of this Node object

getValue

Return the value of the immediate child of this Node object if a child exists and its value is text

recycleNode()

Notify the implementation that his Node object is no longer being used and is free for reuse

setParentElement(SOAPElement)

Set the parent of this object to that specified by the SOAPElement parameter

Namespaces

An XML namespace is a means of qualifying element and attribute names to disambiguate them from other names in the same document. This section provides a brief description of XML namespaces and how they are used in SOAP. For complete information, see http://www.w3.org/TR/REC-xml-names/

An explicit XML namespace declaration takes the following form:

<prefix:myElement
xmlns:prefix ="URI">

The declaration defines prefix as an alias for the specified URI. In the element myElement, you can use prefix with any element or attribute to specify that the element or attribute name belongs to the namespace specified by the URI.

The following is an example of a namespace declaration:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"

This declaration defines SOAP_ENV as an alias for the namespace:

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

After defining the alias, you can use it as a prefix to any attribute or element in the Envelope element. In Example 5–1, the elements <Envelope> and <Body> and the attribute encodingStyle all belong to the SOAP namespace specified by the http://schemas.sxmlsoap.org/soap/envelope/URI .

Example 5–1 Explicit Namespace Declarations

<SOAP-ENV:Envelope
   xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
   SOAP-ENV:encodingStyle=
                     "http://schemas.xmlsoap.org/soap/encoding/">
   <SOAP-ENV:Header>
        <HeaderA
 xmlns="HeaderURI"
 SOAP-ENV:mustUnderstand="0">
     
      The text of the header
     </HeaderA>
 </SOAP-ENV:Header>
   <SOAP-ENV:Body>
.
.
.
   </SOAP-ENV:Body>
 </SOAP-ENV:Envelope>

Note that the URI that defines the namespace does not have to point to an actual location; its purpose is to disambiguate attribute and element names.

Pre-defined SOAP Namespaces

SOAP defines two namespaces:

The SOAP envelope, the root element of a SOAP message, has the following namespace identifier:
```
"http://schemas.xmlsoap.org/soap/envelope"
```
The SOAP serialization, the URI defining SOAP’s serialization rules, has the following namespace identifier:
```
"http://schemas.xmlsoap.org/soap/encoding"
```

When you use SAAJ to construct or consume messages, you are responsible for setting or processing namespaces correctly and for discarding messages that have incorrect namespaces.

Using Namespaces when Creating a SOAP Name

When you create the body elements or header elements of a SOAP message, you must use the Name object to specify a well-formed name for the element. You obtain a Name object by calling the method SOAPEnvelope.createName.

When you call this method, you can pass a local name as a parameter or you can specify a local name, prefix, and URI. For example, the following line of code defines a name object bodyName.

Name bodyName = MyEnvelope.createName("TradePrice",
                                 "GetLTP","http://foo.eztrade.com");

This would be equivalent to the namespace declaration:

<GetLTP:TradePrice xmlns:GetLTP= "http://foo.eztrade.com">

The following code shows how you create a name and associate it with a SOAPBody element. Note the use and placement of the createName method.

SoapBody body = envelope.getBody();//get body from envelope
Name bodyName = envelope.createName("TradePrice", "GetLTP",
                                        "http://foo.eztrade.com");
SOAPBodyElement gltp = body.addBodyElement(bodyName);

Parsing Name Objects

For any given Name object, you can use the following Name methods to parse the name:

getQualifiedName returns "prefix:LocalName ", for the given name, this would be GetLTP:TradePrice.
getURI would return "http://foo.eztrade.com" .
getLocalName would return "TradePrice ".
getPrefix would return "GetLTP".