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javamemoryantheap-memory

What does maxmemory flag in Apache Ant java target exactly do?

Take the following build.xml snippet:

  <target name="run">
      <java
        jar="${server-jar}"
        fork="true"
        failonerror="true"
        maxmemory="1g">
          <jvmarg line="${env.JVM_ARGS}"/>
      </java>
  </target>

What does the maxmemory flag exactly do? Does it set the heap memory initial/max size? I get heap errors and trying to understand if this flag is enough, or I must set -Xmx and -Xms separately in JVM_ARGS.

The documentation of maxmemory in ant java target is vague to me:

maxmemory: Max amount of memory to allocate to the forked JVM, ignored if fork is false

Solution

  • According to the JavaDoc for the Java task class:

    Corresponds to -mx or -Xmx depending on VM version.

    In the source code, it is referenced here.

    And, yes, Xmx is the setting for the heap:

    Specifies the maximum size (in bytes) of the heap.

    (You may see a bit more info about some of the other Ant <java> task settings, too, in the Javadoc.)