I cant get lcm-spy to decode lcm messages

[Benjamin Fain]

I have lcm messages that were created using python. Since lcm-spy needs a jar file I have recreated the lcm definition files into java and tried turning them into .jars. I also tried to do this with just the example_t.lcm and I keep getting errors on the "javac -cp lcm.jar exlcm/*.java" part.

suas@suas:~/Desktop/LCM_EXP$ javac -cp lcm.jar exlcm/*.java
exlcm/example_t.java:10: package lcm.lcm does not exist
import lcm.lcm.*;
^
exlcm/example_t.java:12: package lcm.lcm does not exist
public final class example_t implements lcm.lcm.LCMEncodable
                                               ^
exlcm/example_t.java:80: cannot find symbol
symbol  : class LCMDataInputStream
location: class exlcm.example_t
        this(new LCMDataInputStream(data));
                 ^
exlcm/example_t.java:78: recursive constructor invocation
    public example_t(byte[] data) throws IOException
           ^
4 errors

------
Not sure why it cannot find lcm.lcm


Thanks for the help!

[Benjamin Fain]

I also have Java 1.6 installed as I found 1.7 or 1.8 could give problems based on the forum

suas@suas:~$ java -version
java version "1.6.0_39"
OpenJDK Runtime Environment (IcedTea6 1.13.11) (6b39-1.13.11-0ubuntu0.14.04.1)
OpenJDK 64-Bit Server VM (build 23.25-b01, mixed mode)

[Jonathan Bendes]

Hey Ben,

Did you make sure that you're pointing to the correct lcm.jar file during your attempted javac of your java files? Can you open that .jar file with a file browser and make sure it contains the lcm java files?

Best,

Jonathan

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[Benjamin Fain]

Jonathan,
Thanks for the response.
After it kept erroring out on import lcm.lcm.* I opened the .Java in the exclum folder to find import lcm.lcm.* to be where it keeps erroring. I was not able to locate an lcm.jar file to point Java to. In the lcm install folder I could not find it. Only lcm-logger, lcm-logger and others where there. Internet searchs also did not help me. Is it an extra I have to download from git?

Regards,
Ben

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[Benjamin Fain]

Also this is on Ubuntu the 14.04. And I have upgrade to Java 1.7 but can revert.

[Jonathan Bendes]

Hey Ben,

You built the jar when you built lcm if you configured your build correctly. Did you follow the steps here?
https://lcm-proj.github.io/build_instructions.html

I am far more familiar with the zcm build tool chain but I believe there may be some parallels. When you built, did you make sure Java was enabled in your build? I believe it should enable automatically if you have java installed and will notify you accordingly in the configure step.

Best,
Jonathan

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[Benjamin Fain]

Jonathan,

Thanks for the help. I had to find the lcm.jar file and then point to it for java to see.

For those finding this question through google you can run the below provided on https://github.com/lcm-proj/lcm/blob/master/examples/lcm-spy/buildjar.sh

For those new to the area like myself the if statements are used to set up the lcm.jar path for java.

I used "export CLASSPATH=/user/local/share/java/lcm.jar" which is the first part of the if statement. I am running ubuntu 14.04 (This only adds the variable to the current terminal you have open!) 

the lcm-gen line assumes you have your types in a folder called ../types. if you are already in the directory just delete the "../types/"

The javac line can be updated to "javac -cp lcm.jar name of folder/*.java" Java can already see lcm.jar now so no need to call the variable in its place.

The last line creates the jar with name "my_types" assuming the folder name is exlcm.

Also this works with java 1.6 and 1.7 (not sure about 1.8) You also need to make sure you have the java sdk installed (includes javac) and not just the jre. on unbuntu use "java -version" in a terminal.

# try to automatically determine where the LCM java file is
	LCM_JAR=`pkg-config --variable=classpath lcm-java`
	if [ $? != 0 ] ; then
	if [ -e /usr/local/share/java/lcm.jar ] ; then
	LCM_JAR=/usr/local/share/java/lcm.jar
	else
	if [ -e ../../lcm-java/lcm.jar ] ; then
	LCM_JAR=../../lcm-java/lcm.jar
	fi
	fi
	fi
	lcm-gen -j ../types/*.lcm
	javac -cp $LCM_JAR exlcm/*.java
	jar cf my_types.jar exlcm/*.class

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