转：Chapter 5. Creating a Web service with Spring-WS

Chapter 5. Creating a Web service with Spring-WS

5.1. Introduction

Spring-WS's server-side support is designed around a MessageDispatcher that dispatches incoming messages to endpoints, with configurable endpoint mappings, response generation, and endpoint interception. The simplest endpoint is a PayloadEndpoint, which just offers the Source invoke(Source request) method. You are of course free to implement this interface directly, but you will probably prefer to extend one of the included abstract implementations such as AbstractDomPayloadEndpoint, AbstractSaxPayloadEndpoint, and AbstractMarshallingPayloadEndpoint. Alternatively, there is a endpoint development that uses Java 5 annotations, such as @Endpoint for marking a POJO as endpoint, and marking a method with @PayloadRoot or @SoapAction.

Spring-WS's XML handling is extremely flexible. An endpoint can choose from a large amount of XML handling libraries supported by Spring-WS, including the DOM family (W3C DOM, JDOM, dom4j, and XOM), SAX or StAX for faster performance, XPath to extract information from the message, or even marshalling techniques (JAXB, Castor, XMLBeans, JiBX, or XStream) to convert the XML to objects and vice-versa.

5.2. The MessageDispatcher

The server-side of Spring-WS is designed around a central class that dispatches incoming XML messages to endpoints. Spring-WS's MessageDispatcher is extremely flexible, allowing you to use any sort of class as an endpoint, as long as it can be configured in the Spring IoC container. In a way, the message dispatcher resembles Spring's DispatcherServlet, the “Front Controller” used in Spring Web MVC.

The processing and dispatching flow of the MessageDispatcher is illustrated in the following sequence diagram.

The request processing workflow in Spring Web Services

When a MessageDispatcher is set up for use and a request comes in for that specific dispatcher, said MessageDispatcher starts processing the request. The list below describes the complete process a request goes through when handled by a MessageDispatcher:

1. An appropriate endpoint is searched for using the configured EndpointMapping(s). If an endpoint is found, the invocation chain associated with the endpoint (preprocessors, postprocessors, and endpoints) will be executed in order to create a response.

2. An appropriate adapter is searched for the endpoint. The MessageDispatcher delegates to this adapter to invoke the endpoint.

3. If a response is returned, it is sent on its way. If no response is returned (which could be due to a pre- or post-processor intercepting the request, for example, for security reasons), no response is sent.

Exceptions that are thrown during handling of the request get picked up by any of the endpoint exception resolvers that are declared in the application context. Using these exception resolvers allows you to define custom behaviors (such as returning a SOAP Fault) in case such exceptions get thrown.

The MessageDispatcher has several properties, for setting endpoint adapters, mappings, exception resolvers. However, setting these properties is not required, since the dispatcher will automatically detect all of these types that are registered in the application context. Only when detection needs to be overriden, should these properties be set.

The message dispatcher operates on a message context, and not transport-specific input stream and output stream. As a result, transport specific requests need to read into a MessageContext. For HTTP, this is done with a WebServiceMessageReceiverHandlerAdapter, which is a Spring Web HandlerInterceptor, so that the MessageDispatcher can be wired in a standard DispatcherServlet. There is a more convenient way to do this, however, which is shown in Section 5.3.1, “MessageDispatcherServlet”.

5.3. Transports

Spring Web Services supports multiple transport protocols. The most common is the HTTP transport, for which a custom servlet is supplied, but it is also possible to send messages over JMS, and even email.

5.3.1. MessageDispatcherServlet

The MessageDispatcherServlet is a standard Servlet which conveniently extends from the standard Spring Web DispatcherServlet, and wraps a MessageDispatcher. As such, it combines the attributes of these into one: as a MessageDispatcher, it follows the same request handling flow as described in the previous section. As a servlet, the MessageDispatcherServlet is configured in the web.xml of your web application. Requests that you want the MessageDispatcherServlet to handle will have to be mapped using a URL mapping in the same web.xml file. This is standard Java EE servlet configuration; an example of such a MessageDispatcherServlet declaration and mapping can be found below.

    
        spring-ws
        org.springframework.ws.transport.http.MessageDispatcherServlet
        1
    

    
        spring-ws
        /*
    

In the example above, all requests will be handled by the 'spring-ws' MessageDispatcherServlet. This is only the first step in setting up Spring Web Services, because the various component beans used by the Spring-WS framework also need to be configured; this configuration consists of standard Spring XML definitions. Because the MessageDispatcherServlet is a standard Spring DispatcherServlet, it will look for a file named [servlet-name]-servlet.xml in the WEB-INF directory of your web application and create the beans defined there in a Spring container. In the example above, that means that it looks for '/WEB-INF/spring-ws-servlet.xml'. This file will contain all of the SWS-specific beans such as endpoints, marshallers and suchlike.

5.3.1.1. Automatic WSDL exposure

The MessageDispatcherServlet will automatically detect any WsdlDefinition beans defined in it's Spring container. All such WsdlDefinition beans that are detected will also be exposed via a WsdlDefinitionHandlerAdapter; this is a very convenient way to expose your WSDL to clients simply by just defining some beans.

By way of an example, consider the following bean definition, defined in the Spring-WS framework's configuration file ('/WEB-INF/[servlet-name]-servlet.xml'). Take notice of the value of the bean's 'id' attribute, because this will be used when exposing the WSDL.

The WSDL defined in the 'Orders.wsdl' file can then be accessed via GET requests to a URL of the following form (substitute the host, port and servlet context path as appropriate).

http://localhost:8080/spring-ws/orders.wsdl

Note

All WsdlDefinition bean definitions are exposed by the MessageDispatcherServlet under their bean id (or bean name) with the suffix .wsdl. So if the bean id is echo, the host name is "server", and the Servlet context (war name) is "spring-ws", the WSDL can be obtained via http://server/spring-ws/echo.wsdl

Another cool feature of the MessageDispatcherServlet (or more correctly the WsdlDefinitionHandlerAdapter) is that it is able to transform the value of the 'location' of all the WSDL that it exposes to reflect the URL of the incoming request.

Please note that this 'location' transformation feature is off by default.To switch this feature on, you just need to specify an initialization parameter to the MessageDispatcherServlet, like so:

    
        spring-ws
        org.springframework.ws.transport.http.MessageDispatcherServlet
        
            transformWsdlLocations
            true
        
    

    
        spring-ws
        /*
    

Consult the class-level Javadoc on the WsdlDefinitionHandlerAdapter class which explains the whole transformation process in more detail.

As an alternative to writing the WSDL by hand, and exposing it with the SimpleWsdl11Definition, Spring Web Services can also generate a WSDL from an XSD schema. This is the approach shown in Section 3.7, “Publishing the WSDL”. The next application context snippet shows how to create such a dynamic WSDL file:

The DefaultWsdl11Definition which builds a WSDL from a XSD schema. This definition iterates over all element elements found in the schema, and creates a message for all elements. Next, it creates WSDL operation for all messages that end with the defined request or response suffix. The default request suffix is Request; the default response suffix is Response, though these can be changed by setting the requestSuffix and responseSuffix properties, respectively. It also builds a portType, binding, and service based on the operations.

For instance, if our Orders.xsd schema defines the GetOrdersRequest and GetOrdersResponse elements, the XsdBasedSoap11Wsdl4jDefinitionBuilder will create a GetOrdersRequest and GetOrdersResponse message, and a GetOrders operation, which is put in a Orders port type.

If you want to use multiple schemas, either by includes or imports, you might want to use the CommonsXsdSchemaCollection, and refer to that from the DefaultWsdl11Definition, like so:

    
        This bean wrap the messages.xsd (which imports types.xsd), and inlines them as a one.
    
    
        
            /WEB-INF/xsds/Orders.xsd
            /WEB-INF/xsds/Customers.xsd
        
    
    

When the inline property is enabled, it follows all XSD imports and includes, and inlines them in the WSDL. This greatly simplifies the deloyment of the schemas, which still making it possible to edit them separately.

The DefaultWsdl11Definition uses WSDL providers in the org.springframework.ws.wsdl.wsdl11.provider package and the ProviderBasedWsdl4jDefinition to generate a WSDL the first time it is requested. Refer to the class-level Javadoc of these classes to see how you can extend this mechanism, if necessary.

5.3.2. Wiring up Spring-WS in a DispatcherServlet

As an alternative to the MessageDispatcherServlet, you can wire up a MessageDispatcher in a standard, Spring-Web MVC DispatcherServlet. By default, the DispatcherServlet can only delegate to Controllers, but we can instruct it to delegate to a MessageDispatcher by adding a WebServiceMessageReceiverHandlerAdapter to the servlet's web application context:

    

    
        
    
    

    ...

    

Note that by explicitly adding the WebServiceMessageReceiverHandlerAdapter, the dispatcher servlet does not load the default adapters, and is unable to handle standard Spring-MVC Controllers. Therefore, we add the SimpleControllerHandlerAdapter at the end. ^[2]

In a similar fashion, you can wire up a WsdlDefinitionHandlerAdapter to make sure the DispatcherServlet can handle implementations of the WsdlDefinition interface:

    



    
        
           
myServiceDefinition
           
        
        
    

    


       
    

    ...

5.3.3. JMS transport

Spring Web Services supports server-side JMS handling through the JMS functionality provided in the Spring framework. Spring Web Services provides the WebServiceMessageListener to plug in to a MessageListenerContainer. This message listener requires a WebServiceMessageFactory to and MessageDispatcher to operate. The following piece of configuration shows this:

    
        
    

    

    
        
        
        
            
                
                
            
        
    

    
        
                          class="org.springframework.ws.server.endpoint.mapping.PayloadRootQNameEndpointMapping">
                
                    
                
            
        
    

As an alternative to the WebServiceMessageListener, Spring Web Services provides a WebServiceMessageDrivenBean, an EJB MessageDrivenBean. For more information on EJB, refer to the class level Javadocs of the WebServiceMessageDrivenBean.

5.3.4. Email transport

In addition to HTTP and JMS, Spring Web Services also provides server-side email handling. This functionality is provided through the MailMessageReceiver class. This class monitors a POP3 or IMAP folder, converts the email to a WebServiceMessage, sends any response using SMTP. The host names can be configured through the storeUri, which indicates the mail folder to monitor for requests (typically a POP3 or IMAP folder), and a transportUri, which indicates the server to use for sending responses (typically a SMTP server).

How the MailMessageReceiver monitors incoming messages can be configured with a pluggable strategy: the MonitoringStrategy. By default, a polling strategy is used, where the incoming folder is polled for new messages every five minutes. This interval can be changed by setting the pollingInterval property on the strategy. By default, all MonitoringStrategy implementations delete the handled messages; this can be changed by setting the deleteMessages property.

As an alternative to the polling approaches, which are quite inefficient, there is a monitoring strategy that uses IMAP IDLE. The IDLE command is an optional expansion of the IMAP email protocol that allows the mail server to send new message updates to the MailMessageReceiver asynchronously. If you use a IMAP server that supports the IDLE command, you can plug in the ImapIdleMonitoringStrategy into the monitoringStrategy property. In addition to a supporting server, you will need to use JavaMail version 1.4.1 or higher.

The following piece of configuration shows how to use the server-side email support, overiding the default polling interval to a value which checks every 30 seconds (30.000 milliseconds):

    

    
        
        
        
        
        
        
            
                
            
        
    

    
        
                          class="org.springframework.ws.server.endpoint.mapping.PayloadRootQNameEndpointMapping">
                
                    
                
            
        
    

5.3.5. Embedded HTTP Server transport

Spring Web Services provides a transport based on Sun's JRE 1.6 HTTP server. The embedded HTTP Server is a standalone server that is simple to configure. It lends itself to a lighter alternative to conventional servlet containers.

When using the embedded HTTP server, no external deployment descriptor is needed (web.xml). You only need to define an instance of the server and configure it to handle incoming requests. The remoting module in the Core Spring Framework contains a convenient factory bean for the HTTP server: the SimpleHttpServerFactoryBean. The most important property is contexts, which maps context paths to corresponding HttpHandlers.

Spring Web Services provides 2 implementations of the HttpHandler interface: WsdlDefinitionHttpHandler and WebServiceMessageReceiverHttpHandler. The former maps an incoming GET request to a WsdlDefinition. The latter is responsible for handling POST requests for web services messages and thus needs a WebServiceMessageFactory (typically a SaajSoapMessageFactory) and a WebServiceMessageReceiver (typically the SoapMessageDispatcher) to accomplish its task.

To draw parallels with the servlet world, the contexts property plays the role of servlet mappings in web.xml and the WebServiceMessageReceiverHttpHandler is the equivalent of a MessageDispatcherServlet.

The following snippet shows a simple configuration example of the HTTP server transport:

For more information on the SimpleHttpServerFactoryBean, refer to the Javadoc.

5.4. Endpoints

Endpoints are the central concept in Spring-WS's server-side support. Endpoints provide access to the application behavior which is typically defined by a business service interface. An endpoint interprets the XML request message and uses that input to invoke a method on the business service (typically). The result of that service invocation is represented as a response message. Spring-WS has a wide variety of endpoints, using various ways to handle the XML message, and to create a response.

The basis for most endpoints in Spring Web Services is the org.springframework.ws.server.endpoint.PayloadEndpoint interface, the source code of which is listed below.

public interface PayloadEndpoint {

/**
     * Invokes an operation.
     */
    Source invoke(Source request) throws Exception;
}

As you can see, the PayloadEndpoint interface defines a single method that is invoked with the XML payload of a request (typically the contents of the SOAP Body, see Section 4.1.2, “SoapMessage”). The returned Source, if any, is stored in the response XML message. While the PayloadEndpoint interface is quite abstract, Spring-WS offers a lot of endpoint implementations out of the box that already contain a lot of the functionality you might need. The PayloadEndpoint interface just defines the most basic responsibility required of every endpoint; namely handling a request and returning a response.

Alternatively, there is the MessageEndpoint, which operates on a whole MessageContext rather than just the payload. Typically, your code should not be dependent on messages, because the payload should contain the information of interest. Only when it is necessary to perform actions on the message as a whole, such as adding a SOAP header, get an attachment, and so forth, should you need to implement MessageEndpoint, though these actions are usually performed in an endpoint interceptor.

Note

Endpoints, like any other Spring Bean, are scoped as a singleton by default, i.e. one instance of the bean definition is created per container. Being a singleton implies that more than one thread can use it at the same time, so the endpoint has to be thread safe. If you want to use a different scope, such as prototype, refer to the Spring Reference documentation.

Note that all abstract base classes provided in Spring-WS (like AbstractDomPayloadEndpoint etc) are thread safe.

5.4.1. AbstractDomPayloadEndpoint and other DOM endpoints

One of the most basic ways to handle the incoming XML payload is by using a DOM (Document Object Model) API. By extending from AbstractDomPayloadEndpoint, you can use the org.w3c.dom.Element and related classes to handle the request and create the response. When using the AbstractDomPayloadEndpoint as the baseclass for your endpoints you only have to override the invokeInternal(Element, Document) method, implement your logic, and return an Element if a response is necessary. Here is a short example consisting of a class and a declaration in the application context.

package samples;

public class SampleEndpoint extends AbstractDomPayloadEndpoint {

    private String responseText;

    public SampleEndpoint(String responseText) {
        this.responseText = responseText;
    }

    protected Element invokeInternal(
            Element requestElement,
            Document document) throws Exception {
        String requestText = requestElement.getTextContent();
        System.out.println("Request text: " + requestText);

        Element responseElement = document.createElementNS("http://samples", "response");
        responseElement.setTextContent(responseText);
        return responseElement;
    }
}

The above class and the declaration in the application context are all you need besides setting up an endpoint mapping (see the section entitled Section 5.5, “Endpoint mappings”) to get this very simple endpoint working. The SOAP message handled by this endpoint will look something like:

    
        
            Hello
        
    

Though it could also handle the following Plain Old XML (POX) message, since we are only working on the payload of the message, and do not care whether it is SOAP or POX.

    Hello

The SOAP response looks like:

    
        
            Hello World!
        
    

Besides the AbstractDomPayloadEndpoint, which uses W3C DOM, there are other base classes which use alternative DOM APIs. Spring Web Services supports most DOM APIs, so that you can use the one you are familiar with. For instance, the AbstractJDomPayloadEndpoint allows you to use JDOM, and the AbstractXomPayloadEndpoint uses XOM to handle the XML. All of these endpoints have an invokeInternal method similar to above. Also, consider using Spring-WS's XPath support to extract the information you need out of the payload. (See the section entitled Section 4.3, “Handling XML With XPath” for details.)

5.4.2. AbstractMarshallingPayloadEndpoint

Rather than handling XML directly using DOM, you can use marshalling to convert the payload of the XML message into a Java Object. Spring Web Services offers the AbstractMarshallingPayloadEndpoint for this purpose, which is built on the marshalling abstraction described in Chapter 8, Marshalling XML using O/X Mappers. The AbstractMarshallingPayloadEndpoint has two properties: marshaller and unmarshaller, in which you can inject in the constructor or by setters.

When extending from AbstractMarshallingPayloadEndpoint, you have to override the invokeInternal(Object) method, where the passed Object represents the unmarshalled request payload, and return an Object that will be marshalled into the response payload. Here is an example:

package samples;

import org.springframework.oxm.Marshaller;
import org.springframework.oxm.Unmarshaller;

public class MarshallingOrderEndpoint extends AbstractMarshallingPayloadEndpoint{

    private final OrderService orderService;

    public MarshallingOrderEndpoint(OrderService orderService, Marshaller marshaller) {
        super(marshaller);
        this.orderService = orderService;
    }

    protected Object invokeInternal(Object request) throws Exception {
        OrderRequest orderRequest = (OrderRequest) request;
        Order order = orderService.getOrder(orderRequest.getId());
        return order;
    }
}

    
        
        
    

    
        
            
                samples.OrderRequest
                samples.Order
            
        
    

    

In this sample, we configure a Jaxb2Marshaller for the OrderRequest and Order classes, and inject that marshaller together with the DefaultOrderService into our endpoint. This business service is not shown, but it is a normal transactional service, probably using DAOs to obtain data from a database. In the invokeInternal method, we cast the request object to an OrderRequest object, which is the JAXB object representing the payload of the request. Using the identifier of that request, we obtain an order from our business service and return it. The returned object is marshalled into XML, and used as the payload of the response message. The SOAP request handled by this endpoint will look like:

The resulting response will be something like:

    
        
            
                1
                20.0
            
            
                1
                10.0
            
        
    

Instead of JAXB 2, we could have used any of the other marshallers described in Chapter 8, Marshalling XML using O/X Mappers. The only thing that would change in the above example is the configuration of the marshaller bean.

5.4.3. Using Spring Validator with Marshalling Endpoints

It is possible to use Validator objects in conjunction with marshalling endpoints in order to validate the unmarshalled payloads. Spring-WS provides 2 extensions of AbstractMarshallingPayloadEndpoint for that purpose: AbstractValidatingMarshallingPayloadEndpoint and AbstractFaultCreatingValidatingMarshallingPayloadEndpoint. The former is the most general whereas the latter specializes in creating SOAP faults in response to validation errors.

Both classes support setting one or more Validator objects via the validator and validators properties respectively. Note that all of the injected validators must support the request object (through the supports method) or else an IllegalArgumentException will be thrown.

Note

The default request object name used in the validator is request. The error codes are generated in consequence. For instance, assuming a POJO with a "name" property of type java.lang.String, calling errors.rejectValue("name","invalidValue") in the validate method of a Validator generates the following error codes: invalidValue.request.name, invalidValue.name, invalidValue.java.lang.String and invalidValue. Similarly, calling errors.reject("invalidValue") generates invalidValue.request and invalidValue as error codes.

5.4.3.1. AbstractValidatingMarshallingPayloadEndpoint

Subclasses of AbstractValidatingMarshallingPayloadEndpoint implement the validation error handling logic by overriding the onValidationErrors method. This method is called when a validation error occurs and its return value indicates whether the endpoint should continue processing the request or not.

In the following example, a custom error POJO is marshalled and sent as a response:

public class MyMarshallingEndpoint extends AbstractValidatingMarshallingPayloadEndpoint{

    private MessageSource messageSource;

    protected Object invokeInternal(Object requestObject) throws Exception {
    	// process the payload
    }

    protected boolean onValidationErrors(MessageContext messageContext, Object requestObject, Errors errors) {
        FieldError error = errors.getFieldError("name");
        CustomError customError = new CustomError();
        String message = messageSource.getMessage(error, Locale.ENGLISH);
        customError.setMessage(message);
        try {
            getMarshaller().marshal(customError, messageContext.getResponse().getPayloadResult());
        } catch (XmlMappingException ex) {
            // handle the exception
        } catch (IOException ex) {
            // handle the exception
        }
        return false;
    }
}

5.4.3.2. AbstractFaultCreatingValidatingMarshallingPayloadEndpoint

Endpoints of this type generate a SOAP fault whenever a validation error occurs. By default, a fault detail element is generated for each validation error. The error codes are resolved using the application context message source.

The properties of AbstractFaultCreatingValidatingMarshallingPayloadEndpoint have sensible defaults, which makes its subclasses quite simple to configure as in the following example:

In case of validation error, here is how the response might look like:

   
   
      
         SOAP-ENV:Client
         Validation error
         
            
                invalid user id: Ernie
            
            
                invalid order
            
         
      
   

It is possible though to customize various aspects of the generated SOAP faults, such as the fault string and the soap detail. Please refer to the Javadoc for the full list of available options.

5.4.4. @Endpoint

The previous two programming models were based on inheritance, and handled individual XML messages. Spring Web Services offer another endpoint with which you can aggregate multiple handling into one controller, thus grouping functionality together. This model is based on annotations, so you can use it only with Java 5 and higher. Here is an example that uses the same marshalled objects as above:

package samples;

import org.springframework.ws.server.endpoint.annotation.Endpoint;
import org.springframework.ws.server.endpoint.annotation.PayloadRoot;

@Endpoint
public class AnnotationOrderEndpoint {
    private final OrderService orderService;

    public AnnotationOrderEndpoint(OrderService orderService) {
        this.orderService = orderService;
    }

    @PayloadRoot(localPart = "orderRequest", namespace = "http://samples")
    public Order getOrder(OrderRequest orderRequest) {
        return orderService.getOrder(orderRequest.getId());
    }

    @PayloadRoot(localPart = "order", namespace = "http://samples")
    public void order(Order order) {
        orderService.createOrder(order);
    }

}

By annotating the class with @Endpoint, you mark it as a Spring-WS endpoint. Because the endpoint class can have multiple request handling methods, we need to instruct Spring-WS which method to invoke for which request. This is done using the @PayloadRoot annotation: the getOrder method will be invoked for requests with a orderRequest local name and a http://samples namespace URI; the order method for requests with a order local name. For more information about these annotations, refer to Section 5.5.3, “MethodEndpointMapping”. We also need to configure Spring-WS to support the JAXB objects OrderRequest and Order by defining a Jaxb2Marshaller:

    
        
    

    

    
        
    

    
        
            
                samples.OrderRequest
                samples.Order
            
                
    

    

The GenericMarshallingMethodEndpointAdapter converts the incoming XML messages to marshalled objects used as parameters and return value; the PayloadRootAnnotationMethodEndpointMapping is the mapping that detects and handles the @PayloadRoot annotations.

5.4.4.1. @XPathParam

As an alternative to using marshalling, we could have used XPath to extract the information out of the incoming XML request. Spring-WS offers another annotation for this purpose: @XPathParam. You simply annotate one or more method parameter with this annotation (each), and each such annotated parameter will be bound to the evaluation of that annotation. Here is an example:

package samples;

import javax.xml.transform.Source;

import org.springframework.ws.server.endpoint.annotation.Endpoint;
import org.springframework.ws.server.endpoint.annotation.PayloadRoot;
import org.springframework.ws.server.endpoint.annotation.XPathParam;

@Endpoint
public class AnnotationOrderEndpoint {

    private final OrderService orderService;

    public AnnotationOrderEndpoint(OrderService orderService) {
        this.orderService = orderService;
    }

    @PayloadRoot(localPart = "orderRequest", namespace = "http://samples")
    public Source getOrder(@XPathParam("/s:orderRequest/@id") double orderId) {
        Order order = orderService.getOrder((int) orderId);
// create Source from order and return it
    }

}

Since we use the prefix 's' in our XPath expression, we must bind it to the http://samples namespace:

    
        
    

    

    


        
            
                http://samples
            
        
    

Using the @XPathParam, you can bind to all the data types supported by XPath:

• boolean or Boolean

• double or Double

• String

• Node

• NodeList

5.5. Endpoint mappings

The endpoint mapping is responsible for mapping incoming messages to appropriate endpoints. There are some endpoint mappings you can use out of the box, for example, the PayloadRootQNameEndpointMapping or the SoapActionEndpointMapping, but let's first examine the general concept of an EndpointMapping.

An EndpointMapping delivers a EndpointInvocationChain, which contains the endpoint that matches the incoming request, and may also contain a list of endpoint interceptors that will be applied to the request and response. When a request comes in, the MessageDispatcher will hand it over to the endpoint mapping to let it inspect the request and come up with an appropriate EndpointInvocationChain. Then the MessageDispatcher will invoke the endpoint and any interceptors in the chain.

The concept of configurable endpoint mappings that can optionally contain interceptors (which can manipulate the request or the response, or both) is extremely powerful. A lot of supporting functionality can be built into custom EndpointMappings. For example, there could be a custom endpoint mapping that chooses an endpoint not only based on the contents of a message, but also on a specific SOAP header (or indeed multiple SOAP headers).

Most endpoint mappings inherit from the AbstractEndpointMapping, which offers an 'interceptors' property, which is the list of interceptors to use. EndpointInterceptors are discussed in Section 5.5.5, “Intercepting requests - the EndpointInterceptor interface”. Additionally, there is the 'defaultEndpoint', which is the default endpoint to use, when this endpoint mapping does not result in a matching endpoint.

5.5.1. PayloadRootQNameEndpointMapping

The PayloadRootQNameEndpointMapping will use the qualified name of the root element of the request payload to determine the endpoint that handles it. A qualified name consists of a namespace URI and a local part, the combination of which should be unique within the mapping. Here is an example:

    
        
            
                getOrderEndpoint
                createOrderEndpoint
            
        
    

    
        
    

    
        
    

The qualified name is expressed as { + namespace URI + } + local part. Thus, the endpoint mapping above routes requests for which have a payload root element with namespace http://samples and local part orderRequest to the 'getOrderEndpoint'. Requests with a local part order will be routed to the 'createOrderEndpoint'.

5.5.2. SoapActionEndpointMapping

Rather than base the routing on the contents of the message with the PayloadRootQNameEndpointMapping, you can use the SOAPAction HTTP header to route messages. Every client sends this header when making a SOAP request, and the header value used for a request is defined in the WSDL. By making the SOAPAction unique per operation, you can use it as a discriminator. Here is an example:

    
        
            
                getOrderEndpoint
                createOrderEndpoint
            
        
    

    
        
    

    
        
    

The mapping above routes requests which have a SOAPAction of http://samples/RequestOrder to the 'getOrderEndpoint'. Requests with http://samples/CreateOrder will be routed to the 'createOrderEndpoint'.

Caution

Note that using SOAP Action headers is SOAP 1.1-specific, so it cannot be used when using Plain Old XML, nor with SOAP 1.2.

5.5.3. MethodEndpointMapping

As explained in Section 5.4.4, “@Endpoint”, the @Endpoint style allows you to handle multiple requests in one endpoint class. This is the responsibility of the MethodEndpointMapping. Similar to the endpoint mapping described above, this mapping determines which method is to be invoked for an incoming request message.

There are two endpoint mappings that can direct requests to methods: the PayloadRootAnnotationMethodEndpointMapping and the SoapActionAnnotationMethodEndpointMapping, both of which are very similar to their non-method counterparts described above.

The PayloadRootAnnotationMethodEndpointMapping uses the @PayloadRoot annotation, with the localPart and namespace elements, to mark methods with a particular qualified name. Whenever a message comes in which has this qualified name for the payload root element, the method will be invoked. For an example, see above.

Alternatively, the SoapActionAnnotationMethodEndpointMapping uses the @SoapAction annotation to mark methods with a particular SOAP Action. Whenever a message comes in which has this SOAPAction header, the method will be invoked.

5.5.4. WS-Addressing

WS-Addressing specifies a transport-neutral routing mechanism. It is based on a To and Action SOAP header, which indicate the destination and intent of the SOAP message, respectively. Additionally, WS-Addressing allows you to define a return address (for normal messages and for faults), and a unique message identifier which can be used for correlation ^[3]. Here is an example of a WS-Addressing message:

    xmlns:wsa="http://www.w3.org/2005/08/addressing">
    
        urn:uuid:21363e0d-2645-4eb7-8afd-2f5ee1bb25cf
        
            http://example.com/business/client1
        
        http://example/com/fabrikam
        http://example.com/fabrikam/mail/Delete
    
    
        
            42
        
    

In this example, the destination is set to http://example/com/fabrikam, while the action is set to http://example.com/fabrikam/mail/Delete. Additionally, there is a message identifier, and an reply-to address. By default, this address is the "anonymous" address, indicating that a response should be sent using the same channel as the request (i.e. the HTTP response), but it can also be another address, as indicated in this example.

In Spring Web Services, WS-Addressing is implemented as an endpoint mapping. Using this mapping, you associate WS-Addressing actions with endpoints, similar to the SoapActionEndpointMapping described above.

5.5.4.1. SimpleActionEndpointMapping

The SimpleActionEndpointMapping is meant to be used in a standard Spring application context. It maps actions to endpoints via an exposed mappings property. Here is an example:

    
        
            
                getOrderEndpoint
                createOrderEndpoint
            
        
    

    
        
    

    
        
    

The mapping above routes requests which have a WS-Addressing Action of http://samples/RequestOrder to the 'getOrderEndpoint'. Requests with http://samples/CreateOrder will be routed to the 'createOrderEndpoint'.

By default, the SimpleActionEndpointMapping supports both the 1.0 (May 2006), and the August 2004 editions of WS-Addressing. These two versions are most popular, and are interoperably with Axis 1 and 2, JAX-WS, XFire, Windows Communication Foundation (WCF), and Windows Services Enhancemenets (WSE) 3.0. If necessary, specific versions of the spec can be injected into the versions property.

Besides the mappings property, the endpoint mapping also has an address property. If set, value of this property is compared to the To header property of the incominging message.

Finally, there is the messageSenders property, which is required for sending response messages to non-anonymous, out-of-bound addresses. You can set MessageSender implementations in this property, the same as you would on the WebServiceTemplate. See Section 6.2.1.1, “URIs and Transports”.

5.5.4.2. AnnotationActionEndpointMapping

The AnnotationActionEndpointMapping is quite similar to the SimpleActionEndpointMapping. It has the same versions and messageSenders properties, but uses Java 5 annotations.

To use the AnnotationActionEndpointMapping, annotate the handling methods with the @Action annotation, similar to the @PayloadRoot and @SoapAction annotations described in Section 5.4.4, “@Endpoint” and Section 5.5.3, “MethodEndpointMapping”. Here is an example:

package samples;

import org.springframework.ws.server.endpoint.annotation.Endpoint;
import org.springframework.ws.soap.addressing.server.annotation.Action

@Endpoint
public class AnnotationOrderEndpoint {
    private final OrderService orderService;

    public AnnotationOrderEndpoint(OrderService orderService) {
        this.orderService = orderService;
    }

    @Action("http://samples/RequestOrder")
    public Order getOrder(OrderRequest orderRequest) {
        return orderService.getOrder(orderRequest.getId());
    }

    @Action("http://samples/CreateOrder")
    public void order(Order order) {
        orderService.createOrder(order);
    }

}

In addition to the @Action annotation, you can annotate the class with the @Address annotation. If set, the value is compared to the To header property of the incominging message.

5.5.5. Intercepting requests - the EndpointInterceptor interface

The endpoint mapping mechanism has the notion of endpoint interceptors. These can be extremely useful when you want to apply specific functionality to certain requests, for example, dealing with security-related SOAP headers, or the logging of request and response message.

Interceptors located in the endpoint mapping must implement the EndpointInterceptor interface from the org.springframework.ws.server package. This interface defines three methods, one that can be used for handling the request message before the actual endpoint will be executed, one that can be used for handling a normal response message, and one that can be used for handling fault messages, both of which will be called after the endpoint is executed. These three methods should provide enough flexibility to do all kinds of pre- and post-processing.

The handleRequest(..) method on the interceptor returns a boolean value. You can use this method to interrupt or continue the processing of the invocation chain. When this method returns true, the endpoint execution chain will continue, when it returns false, the MessageDispatcher interprets this to mean that the interceptor itself has taken care of things and does not continue executing the other interceptors and the actual endpoint in the invocation chain. The handleResponse(..) and handleFault(..) methods also have a boolean return value. When these methods return false, the response will not be sent back to the client.

There are a number of standard EndpointInterceptor implementations you can use in your Web service. Additionally, there is the XwsSecurityInterceptor, which is described in Section 7.2, “ XwsSecurityInterceptor ”.

5.5.5.1. PayloadLoggingInterceptor and SoapEnvelopeLoggingInterceptor

When developing a Web service, it can be useful to log the incoming and outgoing XML messages. SWS facilitates this with the PayloadLoggingInterceptor and SoapEnvelopeLoggingInterceptor classes. The former logs just the payload of the message to the Commons Logging Log; the latter logs the entire SOAP envelope, including SOAP headers. The following example shows you how to define them in an endpoint mapping:

            class="org.springframework.ws.server.endpoint.mapping.PayloadRootQNameEndpointMapping">
        
            
                
            
        
        
            
                getOrderEndpoint
                createOrderEndpoint
            
        
    

        class="org.springframework.ws.server.endpoint.interceptor.PayloadLoggingInterceptor"/>

Both of these interceptors have two properties: 'logRequest' and 'logResponse', which can be set to false to disable logging for either request or response messages.

5.5.5.2. PayloadValidatingInterceptor

One of the benefits of using a contract-first development style is that we can use the schema to validate incoming and outgoing XML messages. Spring-WS facilitates this with the PayloadValidatingInterceptor. This interceptor requires a reference to one or more W3C XML or RELAX NG schemas, and can be set to validate requests or responses, or both.

Note

Note that request validation may sound like a good idea, but makes the resulting Web service very strict. Usually, it is not really important whether the request validates, only if the endpoint can get sufficient information to fullfill a request. Validating the response is a good idea, because the endpoint should adhere to its schema. Remember Postel's Law: “Be conservative in what you do; be liberal in what you accept from others.”

Here is an example that uses the PayloadValidatingInterceptor; in this example, we use the schema in /WEB-INF/orders.xsd to validate the response, but not the request. Note that the PayloadValidatingInterceptor can also accept multiple schemas using the schemas property.

        class="org.springframework.ws.soap.server.endpoint.interceptor.PayloadValidatingInterceptor">
    
    
    

5.5.5.3. PayloadTransformingInterceptor

To transform the payload to another XML format, Spring Web Services offers the PayloadTransformingInterceptor. This endpoint interceptor is based on XSLT stylesheets, and is especially useful when supporting multiple versions of a Web service: you can transform the older message format to the newer format. Here is an example to use the PayloadTransformingInterceptor:

        class="org.springframework.ws.server.endpoint.interceptor.PayloadTransformingInterceptor">
    
    

We are simply transforming requests using /WEB-INF/oldRequests.xslt, and response messages using /WEB-INF/oldResponses.xslt. Note that, since endpoint interceptors are registered at the endpoint mapping level, you can simply create a endpoint mapping that applies to the "old style" messages, and add the interceptor to that mapping. Hence, the transformation will apply only to these "old style" message.

5.6. Handling Exceptions

Spring-WS provides EndpointExceptionResolvers to ease the pain of unexpected exceptions occurring while your message is being processed by an endpoint which matched the request. Endpoint exception resolvers somewhat resemble the exception mappings that can be defined in the web application descriptor web.xml. However, they provide a more flexible way to handle exceptions. They provide information about what endpoint was invoked when the exception was thrown. Furthermore, a programmatic way of handling exceptions gives you many more options for how to respond appropriately. Rather than expose the innards of your application by giving an exception and stack trace, you can handle the exception any way you want, for example by returning a SOAP fault with a specific fault code and string.

Endpoint exception resolvers are automatically picked up by the MessageDispatcher, so no explicit configuration is necessary.

Besides implementing the EndpointExceptionResolver interface, which is only a matter of implementing the resolveException(MessageContext, endpoint, Exception) method, you may also use one of the provided implementations. The simplest implementation is the SimpleSoapExceptionResolver, which just creates a SOAP 1.1 Server or SOAP 1.2 Receiver Fault, and uses the exception message as the fault string. The SimpleSoapExceptionResolver is the default, but it can be overriden by explicitly adding another resolver.

5.6.1. SoapFaultMappingExceptionResolver

The SoapFaultMappingExceptionResolver is a more sophisticated implementation. This resolver enables you to take the class name of any exception that might be thrown and map it to a SOAP Fault, like so:

            class="org.springframework.ws.soap.server.endpoint.SoapFaultMappingExceptionResolver">
        
        
            
                org.springframework.oxm.ValidationFailureException=CLIENT,Invalid request
            
        
    

The key values and default endpoint use the format faultCode,faultString,locale, where only the fault code is required. If the fault string is not set, it will default to the exception message. If the language is not set, it will default to English. The above configuration will map exceptions of type ValidationFailureException to a client-side SOAP Fault with a fault string "Invalid request", as can be seen in the following response:

    
       
           SOAP-ENV:Client
           Invalid request
       
    

If any other exception occurs, it will return the default fault: a server-side fault with the exception message as fault string.

5.6.2. SoapFaultAnnotationExceptionResolver

Finally, it is also possible to annotate exception classes with the @SoapFault annotation, to indicate the SOAP Fault that should be returned whenever that exception is thrown. In order for these annotations to be picked up, you need to add the SoapFaultAnnotationExceptionResolver to your application context. The elements of the annotation include a fault code enumeration, fault string or reason, and language. Here is an example exception:

package samples;

import org.springframework.ws.soap.server.endpoint.annotation.FaultCode;
import org.springframework.ws.soap.server.endpoint.annotation.SoapFault;

@SoapFault(faultCode = FaultCode.SERVER)
public class MyBusinessException extends Exception {

    public MyClientException(String message) {
        super(message);
    }
}

Whenever the MyBusinessException is thrown with the constructor string "Oops!" during endpoint invocation, it will result in the following response:

    
       
           SOAP-ENV:Server
           Oops!
       
    

---

^[2] By default, the Spring MVC DispatcherServlet configures the following handler adapters in version 2.5:

• org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter

• org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter

• org.springframework.web.servlet.mvc.throwaway.ThrowawayControllerHandlerAdapter

• org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter

^[3] For more information on WS-Addressing, see http://en.wikipedia.org/wiki/WS-Addressing.

转载于:https://www.cnblogs.com/wenjielee/archive/2010/12/29/1920450.html