Java：尝试编译Hadoop程序时找不到com.sun.tools.javac.Main

Question

When I try to compile my program in Hadoop with this command

bin/hadoop com.sun.tools.javac.Main WordCounter.java

from Hadoop folder, it says

Error: Could not find or load main class com.sun.tools.javac.Main

I looked in similar threads where people suggested to check if JAVA_HOME is properly stated. So in etc/hadoop/hadoop-env.sh I added this line

export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64

then checked if tools.pack is properly unpacked in /usr/lib/jvm/java-7-openjdk-amd64/lib and it was. Then I tried javac -version which gave

javac 1.7.0_65

I tried to reinstall Java but it didn't solve the problem.

Answer 1

尝试设置HADOOP_CLASSPATH环境变量

export HADOOP_CLASSPATH=$JAVA_HOME/lib/tools.jar

Answer 2

The error means you don't use a JDK to start Hadoop. The main difference between the JRE (pure runtime) and the JDK is the Java compiler javac . To see if you have a Java compiler, you need to check two places: There should be a javac in the $JAVA_HOME/bin folder plus there must be a file $JAVA_HOME/lib/tools.jar .

In your case, the first one (the binary to start the compiler) can be missing but you absolutely need the tools.jar .

You say that you have a tools.pack but I haven't heard about this one before. Use your package manager to search for openjdk and then look for a package in the result list which says jdk . On my system, that would be openjdk-7-jdk . Install this package and the error should go away.

Answer 3

I had to downgrade Hadoop to 2.9.2 and it's working.

I also had these in my environment:

export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk
export PATH=${JAVA_HOME}/bin:${PATH}
export HADOOP_CLASSPATH=${JAVA_HOME}/lib/tools.jar