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Chapter 42. Working with Contexts
Abstract
JAX-WS uses contexts to pass metadata along the messaging chain. This metadata, depending on its scope, is accessible to implementation level code. It is also accessible to JAX-WS handlers that operate on the message below the implementation level.
42.1. Understanding Contexts
Overview
In many instances it is necessary to pass information about a message to other parts of an application. Apache CXF does this using a context mechanism. Contexts are maps that hold properties relating to an outgoing or an incoming message. The properties stored in the context are typically metadata about the message, and the underlying transport used to communicate the message. For example, the transport specific headers used in transmitting the message, such as the HTTP response code or the JMS correlation ID, are stored in the JAX-WS contexts.
The contexts are available at all levels of a JAX-WS application. However, they differ in subtle ways depending upon where in the message processing stack you are accessing the context. JAX-WS Handler implementations have direct access to the contexts and can access all properties that are set in them. Service implementations access contexts by having them injected, and can only access properties that are set in the APPLICATION
scope. Consumer implementations can only access properties that are set in the APPLICATION
scope.
Figure 42.1, “Message Contexts and Message Processing Path” shows how the context properties pass through Apache CXF. As a message passes through the messaging chain, its associated message context passes along with it.
Figure 42.1. Message Contexts and Message Processing Path
How properties are stored in a context
The message contexts are all implementations of the javax.xml.ws.handler.MessageContext interface. The MessageContext interface extends the java.util.Map<String key, Object value> interface. Map objects store information as key value pairs.
In a message context, properties are stored as name/value pairs. A property’s key is a String
that identifies the property. The value of a property can be any value stored in any Java object. When the value is returned from a message context, the application must know the type to expect and cast accordingly. For example, if a property’s value is stored in a UserInfo
object it is still returned from a message context as an Object
object that must be cast back into a UserInfo
object.
Properties in a message context also have a scope. The scope determines where a property can be accessed in the message processing chain.
Property scopes
Properties in a message context are scoped. A property can be in one of the following scopes:
APPLICATION
-
Properties scoped as
APPLICATION
are available to JAX-WS Handler implementations, consumer implementation code, and service provider implementation code. If a handler needs to pass a property to the service provider implementation, it sets the property’s scope toAPPLICATION
. All properties set from either the consumer implementation or the service provider implementation contexts are automatically scoped asAPPLICATION
. HANDLER
-
Properties scoped as
HANDLER
are only available to JAX-WS Handler implementations. Properties stored in a message context from a Handler implementation are scoped asHANDLER
by default.
You can change a property’s scope using the message context’s setScope()
method. Example 42.1, “The MessageContext.setScope()
Method” shows the method’s signature.
Example 42.1. The MessageContext.setScope()
Method
setScope
String
key
MessageContext.Scope
scope
java.lang.IllegalArgumentException
The first parameter specifies the property’s key. The second parameter specifies the new scope for the property. The scope can be either:
-
MessageContext.Scope.APPLICATION
-
MessageContext.Scope.HANDLER
Overview of contexts in handlers
Classes that implement the JAX-WS Handler interface have direct access to a message’s context information. The message’s context information is passed into the Handler implementation’s handleMessage()
, handleFault()
, and close()
methods.
Handler implementations have access to all of the properties stored in the message context, regardless of their scope. In addition, logical handlers use a specialized message context called a LogicalMessageContext
. LogicalMessageContext
objects have methods that access the contents of the message body.
Overview of contexts in service implementations
Service implementations can access properties scoped as APPLICATION
from the message context. The service provider’s implementation object accesses the message context through the WebServiceContext object.
For more information see Section 42.2, “Working with Contexts in a Service Implementation”.
Overview of contexts in consumer implementations
Consumer implementations have indirect access to the contents of the message context. The consumer implementation has two separate message contexts:
- Request context — holds a copy of the properties used for outgoing requests
- Response context — holds a copy of the properties from an incoming response
The dispatch layer transfers the properties between the consumer implementation’s message contexts and the message context used by the Handler implementations.
When a request is passed to the dispatch layer from the consumer implementation, the contents of the request context are copied into the message context that is used by the dispatch layer. When the response is returned from the service, the dispatch layer processes the message and sets the appropriate properties into its message context. After the dispatch layer processes a response, it copies all of the properties scoped as APPLICATION
in its message context to the consumer implementation’s response context.
For more information see Section 42.3, “Working with Contexts in a Consumer Implementation”.
42.2. Working with Contexts in a Service Implementation
Overview
Context information is made available to service implementations using the WebServiceContext interface. From the WebServiceContext object you can obtain a MessageContext
object that is populated with the current request’s context properties in the application scope. You can manipulate the values of the properties, and they are propagated back through the response chain.
The MessageContext interface inherits from the java.util.Map interface. Its contents can be manipulated using the Map interface’s methods.
Obtaining a context
To obtain the message context in a service implementation do the following:
- Declare a variable of type WebServiceContext.
-
Decorate the variable with the
javax.annotation.Resource
annotation to indicate that the context information is being injected into the variable. Obtain the
MessageContext
object from the WebServiceContext object using thegetMessageContext()
method.ImportantgetMessageContext()
can only be used in methods that are decorated with the@WebMethod
annotation.
Example 42.2, “Obtaining a Context Object in a Service Implementation” shows code for obtaining a context object.
Example 42.2. Obtaining a Context Object in a Service Implementation
import javax.xml.ws.*; import javax.xml.ws.handler.*; import javax.annotation.*; @WebServiceProvider public class WidgetServiceImpl { @Resource WebServiceContext wsc; @WebMethod public String getColor(String itemNum) { MessageContext context = wsc.getMessageContext(); } ... }
Reading a property from a context
Once you have obtained the MessageContext object for your implementation, you can access the properties stored there using the get()
method shown in Example 42.3, “The MessageContext.get()
Method”.
Example 42.3. The MessageContext.get()
Method
V
get
Object
key
This get()
is inherited from the Map interface.
The key
parameter is the string representing the property you want to retrieve from the context. The get()
returns an object that must be cast to the proper type for the property. Table 42.1, “Properties Available in the Service Implementation Context” lists a number of the properties that are available in a service implementation’s context.
Changing the values of the object returned from the context also changes the value of the property in the context.
Example 42.4, “Getting a Property from a Service’s Message Context” shows code for getting the name of the WSDL operation
element that represents the invoked operation.
Example 42.4. Getting a Property from a Service’s Message Context
import javax.xml.ws.handler.MessageContext; import org.apache.cxf.message.Message; ... // MessageContext context retrieved in a previous example QName wsdl_operation = (QName)context.get(Message.WSDL_OPERATION);
Setting properties in a context
Once you have obtained the MessageContext object for your implementation, you can set properties, and change existing properties, using the put()
method shown in Example 42.5, “The MessageContext.put()
Method”.
Example 42.5. The MessageContext.put()
Method
V
put
K
key
V
value
ClassCastExceptionIllegalArgumentExceptionNullPointerException
If the property being set already exists in the message context, the put()
method replaces the existing value with the new value and returns the old value. If the property does not already exist in the message context, the put()
method sets the property and returns null
.
Example 42.6, “Setting a Property in a Service’s Message Context” shows code for setting the response code for an HTTP request.
Example 42.6. Setting a Property in a Service’s Message Context
import javax.xml.ws.handler.MessageContext; import org.apache.cxf.message.Message; ... // MessageContext context retrieved in a previous example context.put(Message.RESPONSE_CODE, new Integer(404));
Supported contexts
Table 42.1, “Properties Available in the Service Implementation Context” lists the properties accessible through the context in a service implementation object.
Property Name | Description |
---|---|
| |
PROTOCOL_HEADERS[a] |
Specifies the transport specific header information. The value is stored as a |
RESPONSE_CODE |
Specifies the response code returned to the consumer. The value is stored as an |
ENDPOINT_ADDRESS |
Specifies the address of the service provider. The value is stored as a |
HTTP_REQUEST_METHOD |
Specifies the HTTP verb sent with a request. The value is stored as a |
PATH_INFO |
Specifies the path of the resource being requested. The value is stored as a
The path is the portion of the URI after the hostname and before any query string. For example, if an endpoint’s URI is http://cxf.apache.org/demo/widgets the path is |
QUERY_STRING |
Specifies the query, if any, attached to the URI used to invoke the request. The value is stored as a
Queries appear at the end of the URI after a |
MTOM_ENABLED |
Specifies whether or not the service provider can use MTOM for SOAP attachments. The value is stored as a |
SCHEMA_VALIDATION_ENABLED |
Specifies whether or not the service provider validates messages against a schema. The value is stored as a |
FAULT_STACKTRACE_ENABLED |
Specifies if the runtime provides a stack trace along with a fault message. The value is stored as a |
CONTENT_TYPE |
Specifies the MIME type of the message. The value is stored as a |
BASE_PATH |
Specifies the path of the resource being requested. The value is stored as a
The path is the portion of the URI after the hostname and before any query string. For example, if an endpoint’s URL is http://cxf.apache.org/demo/widgets the base path is |
ENCODING |
Specifies the encoding of the message. The value is stored as a |
FIXED_PARAMETER_ORDER |
Specifies whether the parameters must appear in the message in a particular order. The value is stored as a |
MAINTAIN_SESSION |
Specifies if the consumer wants to maintain the current session for future requests. The value is stored as a |
WSDL_DESCRIPTION |
Specifies the WSDL document that defines the service being implemented. The value is stored as a |
WSDL_SERVICE |
Specifies the qualified name of the |
WSDL_PORT |
Specifies the qualified name of the |
WSDL_INTERFACE |
Specifies the qualified name of the |
WSDL_OPERATION |
Specifies the qualified name of the |
| |
MESSAGE_OUTBOUND_PROPERTY |
Specifies if a message is outbound. The value is stored as a |
INBOUND_MESSAGE_ATTACHMENTS |
Contains any attachments included in the request message. The value is stored as a The key value for the map is the MIME Content-ID for the header. |
OUTBOUND_MESSAGE_ATTACHMENTS |
Contains any attachments for the response message. The value is stored as a The key value for the map is the MIME Content-ID for the header. |
WSDL_DESCRIPTION |
Specifies the WSDL document that defines the service being implemented. The value is stored as a |
WSDL_SERVICE |
Specifies the qualified name of the |
WSDL_PORT |
Specifies the qualified name of the |
WSDL_INTERFACE |
Specifies the qualified name of the |
WSDL_OPERATION |
Specifies the qualified name of the |
HTTP_RESPONSE_CODE |
Specifies the response code returned to the consumer. The value is stored as an |
HTTP_REQUEST_HEADERS |
Specifies the HTTP headers on a request. The value is stored as a |
HTTP_RESPONSE_HEADERS |
Specifies the HTTP headers for the response. The value is stored as a |
HTTP_REQUEST_METHOD |
Specifies the HTTP verb sent with a request. The value is stored as a |
SERVLET_REQUEST |
Contains the servlet’s request object. The value is stored as a |
SERVLET_RESPONSE |
Contains the servlet’s response object. The value is stored as a |
SERVLET_CONTEXT |
Contains the servlet’s context object. The value is stored as a |
PATH_INFO |
Specifies the path of the resource being requested. The value is stored as a
The path is the portion of the URI after the hostname and before any query string. For example, if an endpoint’s URL is http://cxf.apache.org/demo/widgets the path is |
QUERY_STRING |
Specifies the query, if any, attached to the URI used to invoke the request. The value is stored as a
Queries appear at the end of the URI after a |
REFERENCE_PARAMETERS |
Specifies the WS-Addressing reference parameters. This includes all of the SOAP headers whose |
| |
JMS_SERVER_HEADERS | Contains the JMS message headers. For more information see Section 42.4, “Working with JMS Message Properties”. |
[a]
When using HTTP this property is the same as the standard JAX-WS defined property.
|
42.3. Working with Contexts in a Consumer Implementation
Overview
Consumer implementations have access to context information through the BindingProvider interface. The BindingProvider instance holds context information in two separate contexts:
- Request Context The request context enables you to set properties that affect outbound messages. Request context properties are applied to a specific port instance and, once set, the properties affect every subsequent operation invocation made on the port, until such time as a property is explicitly cleared. For example, you might use a request context property to set a connection timeout or to initialize data for sending in a header.
- Response Context The response context enables you to read the property values set by the response to the last operation invocation made from the current thread. Response context properties are reset after every operation invocation. For example, you might access a response context property to read header information received from the last inbound message.
Only information that is placed in the application scope of a message context can be accessed by the consumer implementation.
Obtaining a context
Contexts are obtained using the javax.xml.ws.BindingProvider interface. The BindingProvider interface has two methods for obtaining a context:
getRequestContext()
ThegetRequestContext()
method, shown in Example 42.7, “ThegetRequestContext()
Method”, returns the request context as aMap
object. The returnedMap
object can be used to directly manipulate the contents of the context.Example 42.7. The
getRequestContext()
MethodMap<String, Object>
getRequestContext
getResponseContext()
ThegetResponseContext()
, shown in Example 42.8, “ThegetResponseContext()
Method”, returns the response context as aMap
object. The returnedMap
object’s contents reflect the state of the response context’s contents from the most recent successful request on a remote service made in the current thread.Example 42.8. The
getResponseContext()
MethodMap<String, Object>
getResponseContext
Since proxy objects implement the BindingProvider interface, a BindingProvider object can be obtained by casting a proxy object. The contexts obtained from the BindingProvider object are only valid for operations invoked on the proxy object used to create it.
Example 42.9, “Getting a Consumer’s Request Context” shows code for obtaining the request context for a proxy.
Example 42.9. Getting a Consumer’s Request Context
// Proxy widgetProxy obtained previously BindingProvider bp = (BindingProvider)widgetProxy; Map<String, Object> requestContext = bp.getRequestContext();
Reading a property from a context
Consumer contexts are stored in java.util.Map<String, Object>
objects. The map has keys that are String
objects and values that contain arbitrary objects. Use java.util.Map.get()
to access an entry in the map of response context properties.
To retrieve a particular context property, ContextPropertyName, use the code shown in Example 42.10, “Reading a Response Context Property”.
Example 42.10. Reading a Response Context Property
// Invoke an operation. port.SomeOperation(); // Read response context property. java.util.Map<String, Object> responseContext = ((javax.xml.ws.BindingProvider)port).getResponseContext(); PropertyType propValue = (PropertyType) responseContext.get(ContextPropertyName);
Setting properties in a context
Consumer contexts are hash maps stored in java.util.Map<String, Object>
objects. The map has keys that are String
objects and values that are arbitrary objects. To set a property in a context use the java.util.Map.put()
method.
While you can set properties in both the request context and the response context, only the changes made to the request context have any impact on message processing. The properties in the response context are reset when each remote invocation is completed on the current thread.
The code shown in Example 42.11, “Setting a Request Context Property” changes the address of the target service provider by setting the value of the BindingProvider.ENDPOINT_ADDRESS_PROPERTY.
Example 42.11. Setting a Request Context Property
// Set request context property. java.util.Map<String, Object> requestContext = ((javax.xml.ws.BindingProvider)port).getRequestContext(); requestContext.put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY, "http://localhost:8080/widgets"); // Invoke an operation. port.SomeOperation();
Once a property is set in the request context its value is used for all subsequent remote invocations. You can change the value and the changed value will then be used.
Supported contexts
Apache CXF supports the following context properties in consumer implementations:
Property Name | Description |
---|---|
| |
ENDPOINT_ADDRESS_PROPERTY |
Specifies the address of the target service. The value is stored as a |
USERNAME_PROPERTY[a] |
Specifies the username used for HTTP basic authentication. The value is stored as a |
PASSWORD_PROPERTY[b] |
Specifies the password used for HTTP basic authentication. The value is stored as a |
SESSION_MAINTAIN_PROPERTY[c] |
Specifies if the client wants to maintain session information. The value is stored as a |
| |
CLIENT_ADDRESSING_PROPERTIES |
Specifies the WS-Addressing information used by the consumer to contact the desired service provider. The value is stored as a |
| |
JMS_CLIENT_REQUEST_HEADERS | Contains the JMS headers for the message. For more information see Section 42.4, “Working with JMS Message Properties”. |
[a]
This property is overridden by the username defined in the HTTP security settings.
[b]
This property is overridden by the password defined in the HTTP security settings.
[c]
The Apache CXF ignores this property.
|
42.4. Working with JMS Message Properties
Abstract
The Apache CXF JMS transport has a context mechanism that can be used to inspect a JMS message’s properties. The context mechanism can also be used to set a JMS message’s properties.
42.4.1. Inspecting JMS Message Headers
Abstract
Consumers and services use different context mechanisms to access the JMS message header properties. However, both mechanisms return the header properties as a org.apache.cxf.transports.jms.context.JMSMessageHeadersType
object.
Getting the JMS Message Headers in a Service
To get the JMS message header properties from the WebServiceContext
object, do the following:
- Obtain the context as described in the section called “Obtaining a context”.
-
Get the message headers from the message context using the message context’s
get()
method with the parameter org.apache.cxf.transports.jms.JMSConstants.JMS_SERVER_HEADERS.
Example 42.12, “Getting JMS Message Headers in a Service Implementation” shows code for getting the JMS message headers from a service’s message context:
Example 42.12. Getting JMS Message Headers in a Service Implementation
import org.apache.cxf.transport.jms.JMSConstants; import org.apache.cxf.transports.jms.context.JMSMessageHeadersType; @WebService(serviceName = "HelloWorldService", portName = "HelloWorldPort", endpointInterface = "org.apache.cxf.hello_world_jms.HelloWorldPortType", targetNamespace = "http://cxf.apache.org/hello_world_jms") public class GreeterImplTwoWayJMS implements HelloWorldPortType { @Resource protected WebServiceContext wsContext; ... @WebMethod public String greetMe(String me) { MessageContext mc = wsContext.getMessageContext(); JMSMessageHeadersType headers = (JMSMessageHeadersType) mc.get(JMSConstants.JMS_SERVER_HEADERS); ... } ... }
Getting JMS Message Header Properties in a Consumer
Once a message is successfully retrieved from the JMS transport you can inspect the JMS header properties using the consumer’s response context. In addition, you can set or check the length of time the client will wait for a response before timing out, as described in the section called “Client Receive Timeout”. To get the JMS message headers from a consumer’s response context do the following:
- Get the response context as described in the section called “Obtaining a context”.
-
Get the JMS message header properties from the response context using the context’s
get()
method with org.apache.cxf.transports.jms.JMSConstants.JMS_CLIENT_RESPONSE_HEADERS as the parameter.
Example 42.13, “Getting the JMS Headers from a Consumer Response Header” shows code for getting the JMS message header properties from a consumer’s response context.
Example 42.13. Getting the JMS Headers from a Consumer Response Header
import org.apache.cxf.transports.jms.context.*; // Proxy greeter initialized previously BindingProvider bp = (BindingProvider)greeter; Map<String, Object> responseContext = bp.getResponseContext(); JMSMessageHeadersType responseHdr = (JMSMessageHeadersType) responseContext.get(JMSConstants.JMS_CLIENT_RESPONSE_HEADERS); ... }
The code in Example 42.13, “Getting the JMS Headers from a Consumer Response Header” does the following:
Casts the proxy to a BindingProvider.
Gets the response context.
Retrieves the JMS message headers from the response context.
42.4.2. Inspecting the Message Header Properties
Standard JMS Header Properties
Table 42.3, “JMS Header Properties” lists the standard properties in the JMS header that you can inspect.
Property Name | Property Type | Getter Method |
---|---|---|
Correlation ID |
|
|
Delivery Mode |
|
|
Message Expiration |
|
|
Message ID |
|
|
Priority |
|
|
Redelivered |
|
|
Time Stamp |
|
|
Type |
|
|
Time To Live |
|
|
Optional Header Properties
In addition, you can inspect any optional properties stored in the JMS header using JMSMessageHeadersType.getProperty()
. The optional properties are returned as a List
of org.apache.cxf.transports.jms.context.JMSPropertyType
. Optional properties are stored as name/value pairs.
Example
Example 42.14, “Reading the JMS Header Properties” shows code for inspecting some of the JMS properties using the response context.
Example 42.14. Reading the JMS Header Properties
// JMSMessageHeadersType messageHdr retrieved previously System.out.println("Correlation ID: "+messageHdr.getJMSCorrelationID()); System.out.println("Message Priority: "+messageHdr.getJMSPriority()); System.out.println("Redelivered: "+messageHdr.getRedelivered()); JMSPropertyType prop = null; List<JMSPropertyType> optProps = messageHdr.getProperty(); Iterator<JMSPropertyType> iter = optProps.iterator(); while (iter.hasNext()) { prop = iter.next(); System.out.println("Property name: "+prop.getName()); System.out.println("Property value: "+prop.getValue()); }
The code in Example 42.14, “Reading the JMS Header Properties” does the following:
Prints the value of the message’s correlation ID.
Prints the value of the message’s priority property.
Prints the value of the message’s redelivered property.
Gets the list of the message’s optional header properties.
Gets an Iterator
to traverse the list of properties.
Iterates through the list of optional properties and prints their name and value.
42.4.3. Setting JMS Properties
Abstract
Using the request context in a consumer endpoint, you can set a number of the JMS message header properties and the consumer endpoint’s timeout value. These properties are valid for a single invocation. You must reset them each time you invoke an operation on the service proxy.
Note that you cannot set header properties in a service.
JMS Header Properties
Table 42.4, “Settable JMS Header Properties” lists the properties in the JMS header that can be set using the consumer endpoint’s request context.
Property Name | Property Type | Setter Method |
---|---|---|
Correlation ID |
|
|
Delivery Mode |
|
|
Priority |
|
|
Time To Live |
|
|
To set these properties do the following:
-
Create an
org.apache.cxf.transports.jms.context.JMSMessageHeadersType
object. - Populate the values you want to set using the appropriate setter methods described in Table 42.4, “Settable JMS Header Properties”.
-
Set the values to the request context by calling the request context’s
put()
method using org.apache.cxf.transports.jms.JMSConstants.JMS_CLIENT_REQUEST_HEADERS as the first argument, and the newJMSMessageHeadersType
object as the second argument.
Optional JMS Header Properties
You can also set optional properties to the JMS header. Optional JMS header properties are stored in the JMSMessageHeadersType
object that is used to set the other JMS header properties. They are stored as a List
object containing org.apache.cxf.transports.jms.context.JMSPropertyType
objects. To add optional properties to the JMS header do the following:
-
Create a
JMSPropertyType
object. -
Set the property’s name field using
setName()
. -
Set the property’s value field using
setValue()
. -
Add the property to the JMS message header using
JMSMessageHeadersType.getProperty().add(JMSPropertyType)
. - Repeat the procedure until all of the properties have been added to the message header.
Client Receive Timeout
In addition to the JMS header properties, you can set the amount of time a consumer endpoint waits for a response before timing out. You set the value by calling the request context’s put()
method with org.apache.cxf.transports.jms.JMSConstants.JMS_CLIENT_RECEIVE_TIMEOUT as the first argument and a long
representing the amount of time in milliseconds that you want the consumer to wait as the second argument.
Example
Example 42.15, “Setting JMS Properties using the Request Context” shows code for setting some of the JMS properties using the request context.
Example 42.15. Setting JMS Properties using the Request Context
import org.apache.cxf.transports.jms.context.*; // Proxy greeter initialized previously InvocationHandler handler = Proxy.getInvocationHandler(greeter); BindingProvider bp= null; if (handler instanceof BindingProvider) { bp = (BindingProvider)handler; Map<String, Object> requestContext = bp.getRequestContext(); JMSMessageHeadersType requestHdr = new JMSMessageHeadersType(); requestHdr.setJMSCorrelationID("WithBob"); requestHdr.setJMSExpiration(3600000L); JMSPropertyType prop = new JMSPropertyType; prop.setName("MyProperty"); prop.setValue("Bluebird"); requestHdr.getProperty().add(prop); requestContext.put(JMSConstants.CLIENT_REQUEST_HEADERS, requestHdr); requestContext.put(JMSConstants.CLIENT_RECEIVE_TIMEOUT, new Long(1000)); }
The code in Example 42.15, “Setting JMS Properties using the Request Context” does the following:
Gets the InvocationHandler
for the proxy whose JMS properties you want to change.
Checks to see if the InvocationHandler
is a BindingProvider
.
Casts the returned InvocationHandler
object into a BindingProvider
object to retrieve the request context.
Gets the request context.
Creates a JMSMessageHeadersType
object to hold the new message header values.
Sets the Correlation ID.
Sets the Expiration property to 60 minutes.
Creates a new JMSPropertyType
object.
Sets the values for the optional property.
Adds the optional property to the message header.
Sets the JMS message header values into the request context.
Sets the client receive timeout property to 1 second.