Use the correct Java JDK for Android builds

NOTE: This blog post was originally hosted on Klocwork’s Android blog. At some point those posts may not continue to exist. I’ve made every attempt to preserve the original content with only formatting changes to fit this site.

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Google released Android 4.3 (Jellybean) source to the AOSP repository a few weeks ago. Whenever this happens, I sync my build box against the AOSP sources. Then I spend some time going through the diffs and run a full Klocwork scan against the code, just to make sure no new problems surface.

I build several Android projects each week and I scan most with our tools. Within certain ranges, I know about how long the builds take and what the distribution of errors looks like. When I started the build for 4.3, I knew I could get on my bike, ride to the deli and grab a sandwich and still have enough time for a peaceful lunch on the patio outside my office.

Needless to say, I didn’t get to enjoy my sandwich as the log files showed the build process lasted less than 2 minutes. The culprit was the build scripts are too smart—they check that I have the correct version of Java installed.

Wait. I have the wrong version of Java installed? There’s only one version of Java that’s allowed with AOSP and that is Sun (Oracle) Java 1.6. There’s no way I would’ve replaced that. I checked java -version and, sure enough, it was Java 1.7.0.21-b11. How did that get in there?

Truth is, there’s no telling. I install and uninstall a lot of software on my build machine and I’m also impatient when it comes to looking at updates. Java 1.6 was still on the machine, it just wasn’t on the path. So, I used the wonderful update-java script that I mentioned in a previous post to set everything back to 1.6.

wget http://webupd8.googlecode.com/files/update-java-0.5b
chmod +x update-java-0.5b
sudo ./update-java-0.5b

I restarted the script and devoted my attention to the muffuletta on my table. I wasn’t two bites into the sandwich when the console window scrolled up, indicating it was finished. I went to the logs and discovered that the $JAVA_HOME value in my .bashrc had changed. [I honestly have no idea how this happened.]{style=”font-size: 13px;”}

# export JAVA_HOME=/usr/lib/jvm/java-6-oracle
export JAVA_HOME=/usr/lib/jvm/java-7-oracle

Maybe I sleep-walk, sleep-copy, sleep-paste, and sleep-edit.

I did what every developer does: I looked for a solution on StackOverflow. From this post, I whipped up a bash script that alerts me before anything else happens. I put this in my .bashrc with a note, but I also have it in the script I use to kick off an Android build.

#!/bin/bash
  # Usage: checkjava.sh [java_version]
  #    if no parameter, script assumes 1.6 (for Android JDK)
  # Returns: 0 for successful match
  #          1 for no Java or wrong Java
  if [ $# -eq 0 ] ; then
    assume="1.6"
  else
    assume=$1
  fi
  typeval=`type -p java`
  if [[ -n $typeval ]] ; then
    _java=java
  elif [[ -n "$JAVA_HOME" ]] && [[ -x "$JAVA_HOME/bin/java" ]];  then
    _java="$JAVA_HOME/bin/java"
  else
    echo "Warning: Java not on PATH"
    exit 1
  fi
  if [[ "$_java" ]]; then
    version=$("$_java" -version 2>&1 | awk -F '"' '/version/ {print $2}')
    jver=${version:0:3}
    if [[ "$jver" != "$assume" ]]; then
    echo "Java version on PATH is $version"
    exit 1
    fi
  fi
  exit 0

Granted, the Android build system will detect this early on, but it takes a couple minutes of figuring out the dependencies before it does the work. I would rather know the moment I open a bash prompt that I may need to give my JDK settings some attention.

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About the Author:

Eric got his start in electronics by disassembling radios at age 10 and putting them back together. Before he could legally drive, he was installing stereos in his friends’ pickups. From there came obsessions with kites, basketball, girls, computers, tools, guitars, baseball, woodworking, photography, golf, and kayaking with varying degrees of success. Eric lives where there are few trees, little water, and no mountains, but he dreams…