Debugging and Logging
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Debugging and Logging

 

 

Logging Messages

CXF uses Java SE Logging for both client- and server-side logging of SOAP requests and responses. Logging is activated by use of separate in/out interceptors that can be attached to the client and/or service as required. These interceptors can be specified either programmatically (via Java code and/or annotations) or via use of configuration files.

Configuration files are probably best. They offer two benefits over programmatic configuration:

  1. Logging requirements can be altered without needing to recompile the code
  2. No Apache CXF-specific APIs need to be added to your code, which helps it remain interoperable with other JAX-WS compliant web service stacks

Enabling message logging through configuration files is shown here.

For programmatic configuration, the logging interceptors can be added to your service endpoint as follows:

For web services running on CXFServlet, the below annotations can be used on either the SEI or the SEI implementation class. If placed on the SEI, they activate logging both for client and server; if on the SEI implementation class, they are relevant just for server-side logging.

or (equivalent)

For programmatic client-side logging, the following code snippet can be used as an example:

Configuring logging levels

In the /etc folder of the CXF distribution there is a sample Java SE logging.properties file you can use to configure logging. For example, if you want to change the console logging level from WARNING to FINE, you need to update two properties in this logging.properties file as below:

Once this is done, you will need to set the -Djava.util.logging.config.file property to the location of the logging.properties file. As an example, the Ant target below has this property set:

Alternatively, for SOAP clients, you can modify the Java-wide logging.properties file in the JDK_HOME/jre/lib folder, or for servlet-hosted web service providers, placing a logging.properties file in the WEB-INF/classes folder (see here for more details.)

Using Log4j Instead of java.util.logging

As noted above, CXF uses the java.util.logging package ("Java SE Logging") by default. But it is possible to switch CXF to instead use Log4J. This is achieved through the use of configuration files. There are two options to bootstrapping CXF logging and each is listed below:

  • Add the following system property to the classpath from which CXF is initialized:
  • Add the file META-INF/cxf/org.apache.cxf.Logger to the classpath and make sure it contains the following content:

Using SLF4J Instead of java.util.logging (since 2.2.8)

As noted above, CXF uses the java.util.logging package by default. But it is possible to switch CXF to instead use SLF4J. This is achieved through the use of configuration files. There are two options to bootstrapping CXF logging and each is listed below:

  • Add the following system property to the classpath from which CXF is initialized:
  • Add the file META-INF/cxf/org.apache.cxf.Logger to the classpath and make sure it contains the following content:

Debugging Tools

Eclipse IDE

See this blog entry for information on debugging web services using Eclipse. Note this is primarily for tracing/debugging source code; you will probably still want to use one of the tools below to capture network traffic, view SOAP requests and responses, etc.

NetBeans IDE

NetBeans include a debugger, profiler and an HTTP monitor that can assist in troubleshooting SOA applications.

tcpmon and tcptrace

tcpmon allows you to easily view messages as they go back and forth on the wire. The companion utility tcptrace can be used for analysis of the dump.

WSMonitor

WSMonitor in another option to Tcpmon with slightly more functionality.

NetSniffer

NetSniffer makes it possible to track the network traffic between arbitrary devices within a LAN segment.

Wireshark

Wireshark, a network packet analyzer, is useful for following the routing of SOAP messages. It can also help when you are getting an HTML error message from the server that your CXF client cannot normally process, by allowing you to see the non-SOAP error message. See this blog entry for more information.

SOAP UI

SOAP UI can also be used for debugging. In addition to viewing messages, it allows you send messages and load test your services. It also has plugins for the Eclipse IDE, NetBeans IDE and IntelliJ IDEA.

Other Helpful Tools

WSDL Viewer

WSDL Viewer is a small tool to visualize web-services in a more intuitive way.

SOAP Fault for debugging

This feature is available since CXF 2.3.4

Stack trace in fault details

CXF supports the ability to put server stack trace information into the fault message fault details, if you enable the option of 'faultStackTraceEnabled'. It is useful for debugging if the soap fault message is not defined in the WSDL operation.

Showing the cause exception message

CXF doesn't show the cause exception message in the fault message due to security consideration. However, this could potentially cause some trouble on the client side, as the client will not be able to see what the real cause of the exception is. You can let the CXF server return the fault message with the embedded cause exception message by enabling the option of 'exceptionMessageCauseEnabled' like this:

ATOM logging

This feature is available since CXF 2.3.0, as part of the cxf-rt-management-web component

CXF supports collecting log events, converting them to ATOM Syndication Format and either pushing them to the Atom-aware consumers or making them available for polling. Logging is based on a custom java.util.logging (JUL) handler that can be registered with loggers extending today's publishing protocols.

CXF JAXRS and JAXWS endpoints can avail of this feature.

Push Style

Push-style handler enqueues log records as they are published from loggers. After the queue size exceeds configurable "batch size", processing of collection of these records (in size of batch size) is triggered. Batch of log events is transformed by converter to ATOM element and then it is pushed out by deliverer to client. Both converter and deliverer are configurable units that allow to change transformation and transportation strategies. Next to predefined own custom implementations can be used when necessary – see examples. Batches are processed sequentially to allow client side to recreate stream of events.

Limitations: Reliability is not supported out of the box, however there is predefined retrying delivery strategy. Persistence is also not supported, any enqueued and undelivered log events are lost on shutdown. Definitions of delivery endpoints is static, subscription of callback URIs is not yet supported.

Spring configuration

In simplest case pushing ATOM Feeds can be declared this way:

Spring bean creates ATOM push handler and registers it with root logger for all log levels. This setup leads to logging everything CXF, Spring and others included. Since batch size is not specified default value of one is used - each event is packed up as single feed pushed out to specified URL. Default conversion strategy and default WebClient-based deliver are used.

More complex example shows how to specify non-root logger and define batch size:

To push to client events generated by different loggers on different levels, "loggers" property must be used instead of pair "logger" and "level":

In example above, second logger does not have specified level, in such case default level of "INFO" is used.

In all above cases, when first delivery fails engine of ATOM push handler is shutdown and no events will be processed and pushed until configuration reload. To avoid this frequent case, retrial can be enabled:

In this case for 5 minutes ("retryTimeout") after delivery failure there will be 1 minute pause ("retryPauseTime") repeated every time with same value ("retryPause" as "linear"). Instead of same pause time, "exponential" value of "retryPause" can be used - each next time pause time doubles. When timeout value is set to 0 retrying is infinite. In case of invalid or missing values defaults are used: for pause time 30 seconds and for timeout 0 (infinite). Instead of same pause time, "exponential" value of "retryPauseType" can be used - each next time pause time doubles. When timeout value is set to 0 retrying is infinite. In case of invalid or missing values defaults are used: for pause time 30 seconds and for timeout 0 (infinite).

Ultimate control is given by "converter" and "deliverer" properties. Either beans of predefined or custom classes can be used (see "Programming syle" chapter for more details). Example below shows custom class using different transport protocol than default:

Note that specifying custom deliverer cause ignoring "url" and "retryXxx" because underneath configuration replaces employed tandem of RetryingDeliverer and WebClientDeliverer with provided one.

When ATOM feeds must be delivered to more than one endpoint and additionally each endpoint is fed by different loggers simply use multiple ATOM push beans in Spring config:

Properties file

When CXF is used either without Spring or logging is configured with properties file, support for this type of configuration becomes handy. ATOM push handler supports "simple configuration" with properties file; simple means aligned to expressiveness of JUL configuration that is limited to cases, where each type of handler can be used only once and registered with root logger.

Set of properties is very similar to Spring configuration with following exceptions:

  • Properties specify classes of custom deliverers and converters, instead of instances.
  • Custom deliverer must have public constructor with the only String parameters; created instance will have passed URL of client.
  • Multiple client endpoints is not supported out of the box (cannot instantiate multiple handlers as in Spring)

Example:

Programming style

In most complex cases direct programming using org.apache.cxf.jaxrs.ext.logging.atom package may be necessary. In this case AtomPushHandler class is main artifact and Deliverer and Converter interfaces and their implementations are necessary components.

Following example:

is equivalent to Spring configuration:

Poll Style

AtomPullServer acts as an Atom feed endpoint and makes all log events it has accumulated or read from some external storage available for polling.

Log events are made available in pages, that is a feed instance will list up to a configurable maximum number of entries and will also include atom links of types 'prev', 'next', 'first' and 'last', thus making it possible to browse through all the log records.

Spring configuration

When configuring AtomPullServer endpoints, one can set the 'loggers' property the same way as it is done for AtomPushBeans, for example :

In addition to the 'loggers' property, a 'pageSize' property limiting a number of entries per page to 30 is also set (default is 40).

One can have a ReadWriteLogStorage bean injected into AtomPushBean if the log records have to be periodically offloaded from memory and persisted across restarts :

When a number of records in memory reaches 400 (default is 500) then the records will be offloaded into a provided storage and will be read from it after the restart or when a client has requested a relevant page. If no storage is available then after an in-memory limit is reached the oldest records will be discarded, one can set a maxInMemorySize property to a large enough value if needed.

Another option is to require a given AtomPullServer to read from the external read-only storage by registering a ReadableLogStorage bean. For example, very often, the runtime is already logging to some external file, thus AtomPullServer can be asked to read from this file only with the help of ReadableLogStorage, without AtomPullServer having to catch log events too.

Once AtomPullServer has been configured, it has to be registered as a service bean with the jaxrs endpoint so that Atom aware clients (blog readers, etc) can start polling it :

Linking to Atom endpoints from CXF Services page

If you would like your users to find about the Atom feeds which are collecting log events from your endpoints then AtomPullServers will need to have a CXF bus injected, as well as be told about the address of the corresponding atom feed endpoint and of the jaxrs or jaxws endpoint :

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  1. Concerning the use of SoapUI as a debugging tool: SoapUI also groks the JAX-RS WADL file. If you open a new project with the URL for your WADL, it will construct a test project with skeleton tests for all the operations defined in the WADL.