type=page status=published title=Debugging Applications next=part-apps-and-app-comps.html prev=class-loaders.html ~~
This chapter gives guidelines for debugging applications in the {productName}.
The following topics are addressed here:
When you enable debugging, you enable both local and remote debugging.
To start the server in debug mode, use the --debug
option as follows:
asadmin start-domain --debug [domain-name]
You can then attach to the server from the Java Debugger (jdb
) at its
default Java Platform Debugger Architecture (JPDA) port, which is 9009.
For example, for UNIX systems:
jdb -attach 9009
For more information about the jdb
debugger, see the following links:
-
Java Platform Debugger Architecture - The Java Debugger:
https://docs.oracle.com/en/java/javase/17/docs/specs/jpda/architecture.html
https://docs.oracle.com/en/java/javase/17/docs/specs/jpda/jpda.html
-
Java Platform Debugger Architecture - Connecting with JDB:
https://docs.oracle.com/en/java/javase/17/docs/specs/man/jdb.html
{productName} debugging is based on the JPDA. For more information, see JPDA Options.
You can attach to the {productName} using any JPDA compliant debugger.
You can enable debugging even when the {productName} is started
without the --debug
option.
This is useful if you start the {productName} from the Windows Start Menu,
or if you want to make sure that debugging is always turned on.
-
Use the Administration Console. Select the JVM Settings component under the relevant configuration.
-
Check the Debug Enabled box.
-
To specify a different port (from 9009, the default) to use when attaching the JVM software to a debugger, specify
address=
port-number in the Debug Options field. -
To add JPDA options, add any desired JPDA debugging options in Debug Options. See JPDA Options.
See Also
For details, click the Help button in the Administration Console from the JVM Settings page.
The default JPDA options in {productName} are as follows:
-Xdebug -agentlib:transport=dt_socket,server=y,suspend=n,address=9009
For Windows, you can change dt_socket
to dt_shmem
.
If you substitute suspend=y
, the JVM software starts in suspended mode
and stays suspended until a debugger attaches to it. This is helpful if
you want to start debugging as soon as the JVM software starts.
To specify a different port (from 9009, the default) to use when attaching the JVM software to a debugger, specify `address=`port-number.
You can include additional options. A list of JPDA debugging options is
available at
http://java.sun.com/javase/technologies/core/toolsapis/jpda/
.
To generate a Java stack trace for debugging, use the
asadmin generate-jvm-report --type=thread
command. The stack trace
goes to the domain-dir`/logs/server.log` file and also appears on the
command prompt screen. For more information about the
asadmin generate-jvm-report
command, see the {productName} Reference Manual.
When the appclient
script executes the java
command to run the
Application Client Container (ACC), which in turn runs the client, it
includes on the command line the value of the VMARGS
environment
variable. You can set this variable to any suitable value. For example:
VMARGS=-agentlib:transport=dt_socket,server=y,suspend=y,address=8118
For debugging an application client, you should set suspend to y
so
you can connect the debugger to the client before any code has actually
executed. Otherwise, the client may start running and execute past the
point you want to examine.
You should use different ports for the server and client if you are debugging both concurrently. For details about setting the port, see JPDA Options.
You can also include JVM options in the appclient
script directly. For
information about the appclient
script, see the {productName} Reference Manual.
Note
|
The Application Client Container is supported only in the full {productName}, not in the Web Profile. See Developing Java Clients. |
Open Message Queue has a broker logger, which can be useful for
debugging Java Message Service (JMS) applications, including
message-driven bean applications. You can adjust the logger’s verbosity,
and you can send the logger output to the broker’s console using the
broker’s -tty
option. For more information, see the Open
Message Queue Administration Guide.
Note
|
JMS resources are supported only in the full {productName}, not in the Web Profile. See Using the Java Message Service. |
To have the server logs and messages printed to System.out
on your
command prompt screen, you can start the server in verbose mode. This
makes it easy to do simple debugging using print statements, without
having to view the server.log
file every time.
To start the server in verbose mode, use the --verbose
option as
follows:
asadmin start-domain --verbose [domain-name]
When the server is in verbose mode, messages are logged to the console
or terminal window in addition to the log file. In addition, pressing
Ctrl-C stops the server and pressing Ctrl-\ (on UNIX platforms) or
Ctrl-Break (on Windows platforms) prints a thread dump. On UNIX
platforms, you can also print a thread dump using the jstack
command
(see
http://docs.oracle.com/javase/8/docs/technotes/tools/share/jstack.html
)
or the command kill -QUIT
process_id.
To generate class loading messages, use the following
asadmin create-jvm-options
command:
asadmin create-jvm-options -verbose\:class
To send the JVM messages to a special JVM log file instead of stdout
,
use the following asadmin create-jvm-options
commands:
asadmin create-jvm-options -XX\:+LogVMOutput
asadmin create-jvm-options -XX\:LogFile=${com.sun.aas.instanceRoot}/logs/jvm.log
Note
|
These |
To send the {productName} messages to the Administration Console
instead of stderr
, start the domain in verbose mode as described in
Enabling Verbose Mode.
You can use the {productName}'s log files to help debug your applications. Use the Administration Console. Select the Stand-Alone Instances component, select the instance from the table, then click the View Log Files button in the General Information page. Or select the Cluster component, select the cluster from the table, select the Instances tab, select the instance from the table, then click the View Log Files button in the General Information page.
To change logging settings, select Logger Settings under the relevant configuration.
For details about logging, click the Help button in the Administration Console.
You can use a profiler to perform remote profiling on the {productName} to discover bottlenecks in server-side performance. This section describes how to configure profilers for use with {productName}.
The following topics are addressed here:
Information about comprehensive monitoring and management support in the
Java 2 Platform, Standard Edition ( J2SE platform) is available at
http://docs.oracle.com/javase/8/docs/technotes/guides/management/index.html
.
For information on how to use the NetBeans profiler, see
http://profiler.netbeans.org/index.html
.
The Heap and CPU Profiling Agent (HPROF) is a simple profiler agent shipped with the Java 2 SDK. It is a dynamically linked library that interacts with the Java Virtual Machine Profiler Interface (JVMPI) and writes out profiling information either to a file or to a socket in ASCII or binary format.
HPROF can monitor CPU usage, heap allocation statistics, and contention
profiles. In addition, it can also report complete heap dumps and states
of all the monitors and threads in the Java virtual machine. For more
details on the HPROF profiler, see the technical article at
http://java.sun.com/developer/technicalArticles/Programming/HPROF.html
.
After HPROF is enabled using the following instructions, its libraries are loaded into the server process.
-
Use the Administration Console. Select the JVM Settings component under the relevant configuration. Then select the Profiler tab.
-
Edit the following fields:
-
Profiler Name -
hprof
-
Profiler Enabled -
true
-
Classpath - (leave blank)
-
Native Library Path - (leave blank)
-
JVM Option - Select Add, type the HPROF JVM option in the Value field, then check its box. The syntax of the HPROF JVM option is as follows:
-Xrunhprof[:help]|[:param=value,param2=value2, ...]
Here is an example of params you can use:
-Xrunhprof:file=log.txt,thread=y,depth=3
The file parameter determines where the stack dump is written.
Using help lists parameters that can be passed to HPROF. The output is as follows:
Hprof usage: -Xrunhprof[:help]|[:<option>=<value>, ...] == Option Name and Value Description Default ----------- ------- heap=dump|sites|all heap profiling all cpu=samples|old CPU usage off format=a|b ascii or binary output a file=<file> write data to file java.hprof (.txt for ascii) net=<host>:<port> send data over a socket write to file depth=<size> stack trace depth 4 cutoff=<value> output cutoff point 0.0001 lineno=y|n line number in traces? y thread=y|n thread in traces? n doe=y|n dump on exit? y
NoteDo not use help in the JVM Option field. This parameter prints text to the standard output and then exits.
The help output refers to the parameters as options, but they are not the same thing as JVM options.
-
-
This writes an HPROF stack dump to the file you specified using the file HPROF parameter.
Information about JProbe from Sitraka is available at
http://www.quest.com/jprobe/
.
After JProbe is installed using the following instructions, its libraries are loaded into the server process.
-
Install JProbe 3.0.1.1. For details, see the JProbe documentation.
-
Configure {productName} using the Administration Console:
-
Select the JVM Settings component under the relevant configuration.
-
Then select the Profiler tab.
-
Edit the following fields before selecting Save and restarting the server:
Profiler Name -jprobe
Profiler Enabled -true
Classpath - (leave blank)
Native Library Path - JProbe-dir/profiler
JVM Option - For each of these options, select Add, type the option in the Value field, then check its box:-Xbootclasspath/p:JProbe-dir/profiler/jpagent.jar -Xrunjprobeagent -Xnoclassgc
NoteIf any of the configuration options are missing or incorrect, the profiler might experience problems that affect the performance of the {productName}.
When the server starts up with this configuration, you can attach the profiler.
-
-
Set the following environment variable:
JPROBE_ARGS_0=-jp_input=JPL-file-path
See Step 6 for instructions on how to create the JPL file.
-
Start the server instance.
-
Launch the
jpprofiler
and attach to Remote Session. The default port is4444
. -
Create the JPL file using the JProbe Launch Pad. Here are the required settings:
-
Select Server Side for the type of application.
-
On the Program tab, provide the following details:
Target Server - other-server
Server home Directory - as-install
Server class File -com.sun.enterprise.server.J2EERunner
Working Directory - as-install
Classpath - as-install/lib/appserv-rt.jar
Source File Path - source-code-dir (in case you want to get the line level details)
Server class arguments - (optional)
Main Package -com.sun.enterprise.server
You must also set VM, Attach, and Coverage tabs appropriately.
For further details, see the JProbe documentation.
After you have created the JPL file, use this an input toJPROBE_ARGS_0
.
-