'Deferred breakpoints: when are classes loaded

I am trying to debug maven with: jdb -attach 8000, after using mvnDebug.
I try to put breakpoints, but get:

main[1] stop in DeployMojo.DeployMojo
Deferring breakpoint DeployMojo.DeployMojo.
It will be set after the class is loaded.
main[1] stop at Dependency:66
Deferring breakpoint Dependency:66.
It will be set after the class is loaded.

When I run, the breakpoints are not called. I have the sources (generated with a maven command), but how can I make them available to the debugger?
Is there a class loader where I could put a breakpoint?

javadebuggingmaven-3jdb


Solution 1:[1]

I was using jdb -attach -sourcepath ~/path/to/project/main/java. Turns out jdb doesn't like the ~ and needs jdb -attach -sourcepath $HOME/path/to/project/main/java or the absolute path.

Solution 2:[2]

For me tibtof's answer was only half what I needed ot make it work. After I explicitly added the package name, jdb would yield "Try compiling with debugging on" on this gradle project of mine:

> Unable to set deferred breakpoint package.ClassName:LineNumber : No linenumber information for package.ClassName.  Try compiling with debugging on.

In this case, if you are using gradle you need to make sure that options.debug=true in the compileJava task, which you can check with the println below.

In my case I was compiling with debugging on - or so I thought. I had my build.gradle like so (based on this answer and this article):

tasks.withType(JavaCompile) {
    options.compilerArgs << '-Xlint:all' << '-Werror' << '-g'
    options.debug = project.hasProperty('debug')
    options.debugOptions.debugLevel = 'source,lines,vars'
    options.debugOptions.debugLevel = 'source,lines,vars'
    doLast {
      println "Args for for $name are $options.allCompilerArgs"
      println "debug=$options.debug"
    }
}

When I ran ./gradlew build -Pdebug it printed as expected:

Args for for compileJava are [-Xlint:all, -Werror, -g]
debug=true

It turns out that when I later run ./gradlew runMyTask --debug-jvm it re-ran the compileJava task because I did not pass -Pdebug again. Running gradle with --info confirms it:

Task ':compileJava' is not up-to-date because:
  Value of input property 'options.debug' has changed for task ':compileJava'

This fact only became apparent after a few hours when I added the aforementioned println:

afarah@gentoopc $ ./gradlew runMyTask --debug-jvm

> Task :compileJava
Args for for compileJava are [-Xlint:all, -Werror, -g]
debug=false

> Task :runMyTask
Listening for transport dt_socket at address: 5005

So the solution was to run ./gradlew runMyTask --debug-jvm -Pdebug, i.e. pass -Pdebug again:

afarah@gentoopc $ ./gradlew runMyTask --debug-jvm -Pdebug

> Task :compileJava
Args for for compileJava are [-Xlint:all, -Werror, -g]
debug=true

> Task :runMyTask
Listening for transport dt_socket at address: 5005

Notice debug=true now, and finally jdb did not complain and stopped at my LineNumber breakpoint.

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Kevin
Solution 2 afarah

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