[CMake] Custom command or custom target for jni?

[Jonatan Bijl]

I am setting up a jni project (Java Native Interface). A java class is
supposed to call native methods, and the native methods are to be
compiled into a dll/so.

To compile the native part, a c header file is generated from the java
class, using the "javah -jni" command. This header file should only be
generated if:

It does not exist yet

The java class changes

 

My first attempt was:

 

set(INTERFACE_HEADER_FILE
${PROJECT_BINARY_DIR}/include/main_java_nl_tba_Testproject_java_HelloWor
ld.h)

set(INTERFACE_JAVA_CLASS main.java.nl.tba.Testproject_Java.HelloWorld)

set(INTERFACE_JAVA_CLASS_FILE
${COMMON_ROOT_BIN_DIRECTORY}/main/java/nl/tba/Testproject_Java/HelloWorl
d.class)

 

add_custom_command(OUTPUT ${INTERFACE_HEADER_FILE}

        COMMAND ${JNI_JAVAH} -jni -d ${PROJECT_BINARY_DIR}/include
${INTERFACE_JAVA_CLASS}

        WORKING_DIRECTORY ${COMMON_ROOT_BIN_DIRECTORY}

       COMMENT "generating jni header file ${INTERFACE_HEADER_FILE}"

        )

set_source_files_properties(HelloWorld.c OBJECT_DEPENDS
${INTERFACE_HEADER_FILE})

add_library(HelloWorldNative SHARED HelloWorld.c
${INTERFACE_HEADER_FILE})

 

cMake however claims there is no rule to make the header file

 

I found somebody who used the following:

add_custom_target(

        HelloWorldNativeHeader

        COMMAND ${JNI_JAVAH} -jni -d ${PROJECT_BINARY_DIR}/include
${INTERFACE_JAVA_CLASS}

        WORKING_DIRECTORY ${COMMON_ROOT_BIN_DIRECTORY}

        COMMENT "generating jni header file ${INTERFACE_HEADER_FILE}"

        )

add_library(HelloWorldNative SHARED HelloWorld.c
${INTERFACE_HEADER_FILE})

add_dependencies(HelloWorldNative HelloWorldNativeHeader)

 

If I understand the documentation correctly, this would force the file
to be generated every time. Is that correct?

 

Which one am I supposed to use? (Cmake 2.6)

If that is the first one, how can I make sure cmake can find the target?

 

Jonatan

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