[[messages]]
== Messages

[[messages-introduction]]
=== Introduction

Messages point out potential problems in the input program; some are
clearly problems (errors), but many more may depend on what the
programmer intends. To keep the noise down the latter are treated as
warnings which can be ignored by the programmer or information which are
hidden. However, when investigating unexpected behavior it's helpful to
show them. This section describes how to configure messages, presents
some problem scenarios when compiling or doing load-time weaving, and
summarizes some of the more relevant messages.

[[messages-introduction-config]]
==== Configuring Messages

The compiler offers `-verbose`, `-warning`, and `-XLint` options when
invoked using the command-line, Ant, or embedded in an IDE. All options
are listed in the AspectJ Development Environment Guide sections for
xref:../devGuideDB/ajc.adoc#ajc[Ajc] and
xref:../devGuideDB/antsupport.adoc#antTasks[Ant Tasks]. The
xref:../devGuideDB/ltw.adoc#ltw[Load-time Weaving] section describes how to
use XML configuration files and system properties to pass options to the
weaver. (You can also pass options to the weaver using system properties
in build- time weaving.) The `-verbose` option has the effect of
including messages level "info", which are normally ignored. Both
`warning` and `XLint` enable you to identify specific messages to emit,
but warning messages tend to be the same provided by the underlying
Eclipse JDT (Java) compiler, while XLint messages are emitted by the
AspectJ compiler or weaver. Obviously, during load-time weaving only
weaver messages will be emitted. Similarly, if aspects are compiled but
not woven, then only compiler messages will be emitted. However, the
usual case for the compiler/weaver working at build time is to emit both
compiler and weaver messages.

The tables below list some options, System Properties (for LTW only) and
Java 5 annotations used to control AspectJ messages. The method of
configuration depends on your environment so please refer to the
relevant documentation for xref:../devGuideDB/ajc.adoc[ajc],
xref:../devGuideDB/antsupport.adoc#antTasks[Ant] or
xref:../devGuideDB/ltw.adoc#weaver-options[LTW].

[cols=",",options="header",]
|===
|Option |Description
|`-verbose` |Show informational messages including AspectJ version and
build date.

|`-debug` |(Load-time weaving only). Show debugging messages such as
which classes are being woven or those that are excluded. (This is not
related to the compiler -g option to include debug information in the
output .class files.)

|`-showWeaveInfo` |Show weaving messages.

|`-Xlint` |Control level of lint messages.

|`messageHolderClass`/ `-XmessageHolderClass:` |In Ant tasks and LTW
respectively specify the class to receive all messages. See
xref:../devGuideDB/antsupport.adoc#antTasks-iajc-options[iajc task
options] or
xref:../devGuideDB/ltw.adoc#weaver-options[Weaver Options].
|===

[cols=",",options="header",]
|===
|System Property |Description
|`aj.weaving.verbose` |Show informational messages including AspectJ
version and build date (same as `-verbose` option).

|`org.aspectj.weaver.showWeaveInfo` |Show weaving messages (same as
`-showWeaveInfo` option).

|`org.aspectj.weaving.messages` |Set this system property to enable
tracing of all compiler messages. See xref:trace.adoc#trace-configuration[Configuring Tracing].
|===

[cols=",",options="header",]
|===
|Annotation |Description
|`@SuppressAjWarnings` |Include this is Java 5 code to suppress AspectJ
warnings associated with the next line of code.
|===

[[messages-scenarios]]
=== Message scenarios

[[messages-scenarios-ct]]
==== Compile-time weaving scenarios

[[messages-scenarios-ct-adviceNotWoven]]
===== Advice not woven

This means that the pointcut for the advice did not match, and it should
be debugged as described in xref:pointcuts.adoc#pointcuts[Debugging Pointcuts].

[[messages-scenarios-ltw]]
==== Load-time weaving scenarios

You can use `META-INF/aop.xml` to control which messages are produced
during LTW. The following example will produce basic informational
messages about the lifecyle of the weaver in addition to any warning or
error messages.

[source, xml]
....
<aspectj>
    <weaver options="-verbose">
    </weaver>
</aspectj>
....

The messages indicate which `META-INF/aop.xml` configurations file(s)
are being used. Each message is also preceeded by the name of the
defining class loader associated with weaver. You can use this
information in a large system to distinguish between different
applications each of which will typically have its own class loader.

[source, text]
....
[AppClassLoader@92e78c] info AspectJ Weaver Version 1.5.3 built on Thursday Oct 26, 2006 at 17:22:31 GMT
[AppClassLoader@92e78c] info register classloader sun.misc.Launcher$AppClassLoader@92e78c
[AppClassLoader@92e78c] info using configuration /C:/temp/META-INF/aop.xml
[AppClassLoader@92e78c] info using configuration /C:/temp/META-INF/aop-ajc.xml
[AppClassLoader@92e78c] info register aspect ExceptionHandler
[AppClassLoader@92e78c] info processing reweavable type ExceptionHandler: ExceptionHandler.aj
....

[[messages-scenarios-ltw-adviceNotWoven]]
===== Advice not woven

It is often difficult to determine, especially when using load-time
weaving (LTW), why advice has not been woven. Here is a quick guide to
the messages to look for. Firstly if you use the `-verbose` option you
should see the following message when your aspect is registered:

[source, text]
....
info register aspect MyAspect
....

Secondly if you use the `-debug` option you should see a message
indicating that you class is being woven:

[source, text]
....
debug weaving 'HelloWorld'
....

However this does not mean that advice has actually been woven into your
class; it says that the class has been passed to the weaver. To
determine whether your pointcuts match you can use the `-showWeaveInfo`
option which will cause a message to be issued each time a join point is
woven:

[source, text]
....
weaveinfo Join point 'method-execution(void HelloWorld.main(java.lang.String[]))' ...
....

If advice is woven at this join point you should get the corresponding
message.

[[messages-xlint]]
=== Lint messages

The table below lists some useful `-Xlint` messages.

[cols=",,",options="header",]
|===
|Message |Default |Description
|`aspectExcludedByConfiguration` |`ignore` |If an aspect is not being
woven, despite being registered, it could be that it has been excluded
by either an `include` or `exclude` element in the `aspects` section of
`META-INF/aop.xml`. Enable this message to determine whether an aspect
has been excluded.

|`adviceDidNotMatch` |`warning` |Issued when advice did not potentially
affect any join points. This means the corresponding pointcut did not
match any join points in the program. This may be valid e.g., in library
aspects or code picking up error conditions, but often the programmer
simply made a mistake in the pointcut. The best approach is to debug the
pointcut.

|`invalidAbsoluteTypeName` |`warning` |Issued when an exact type in a
pointcut does not match any type in the system. Note that this can
interact with the rules for resolving simple types, which permit
unqualified names if they are imported.

|`typeNotExposedToWeaver` |`warning` |This means that a type which could
be affected by an aspect is not available for weaving. This happens when
a class on the classpath should be woven.

|`runtimeExceptionNotSoftened` |`warning` |Before AspectJ 5, declare
soft used to soften runtime exceptions (unnecessarily). Since then, it
does not but does issue this warning in case the programmer did intend
for the exception to be wrapped.

|`unmatchedSuperTypeInCall` |`warning` |Issued when a call pointcut
specifies a defining type which is not matched at the call site (where
the declared type of the reference is used, not the actual runtime
type). Most people should use 'target(Foo) && call(void foo())' instead.
|===
