Java と DAX - Amazon DynamoDB のサンプルJavaアプリを実行したら、"Unsupported major.minor version 52.0" と怒られたので解決策をメモ。
事象
$ java TryDax Exception in thread "main" java.lang.UnsupportedClassVersionError: TryDax : Unsupported major.minor version 52.0 at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:808) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:443) at java.net.URLClassLoader.access$100(URLClassLoader.java:65) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.net.URLClassLoader$1.run(URLClassLoader.java:349) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:348) at java.lang.ClassLoader.loadClass(ClassLoader.java:430) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:323) at java.lang.ClassLoader.loadClass(ClassLoader.java:363) at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)
解決策
- Java のバージョンを確認
$ java -version java version "1.7.0_201" OpenJDK Runtime Environment (amzn-2.6.16.0.78.amzn1-x86_64 u201-b00) OpenJDK 64-Bit Server VM (build 24.201-b00, mixed mode)
- Java のバージョンを 1.8 に変更
$ sudo update-alternatives --config java There are 2 programs which provide 'java'. Selection Command ----------------------------------------------- *+ 1 /usr/lib/jvm/jre-1.7.0-openjdk.x86_64/bin/java 2 /usr/lib/jvm/jre-1.8.0-openjdk.x86_64/bin/java Enter to keep the current selection[+], or type selection number: 2
- Javac は 1.8 だったのでそのまま
$ sudo update-alternatives --config javac There is 1 program that provides 'javac'. Selection Command ----------------------------------------------- *+ 1 /usr/lib/jvm/java-1.8.0-openjdk.x86_64/bin/javac Enter to keep the current selection[+], or type selection number: 1
- コンパイルし直す
$ javac TryDax*.java warning: Supported source version 'RELEASE_7' from annotation processor 'com.amazonaws.eclipse.simpleworkflow.asynchrony.annotationprocessor.AsynchronyDeciderAnnotationProcessor' less than -source '1.8' 1 warning
- サンプルアプリを実行する
$ java TryDax Creating a DynamoDB client Creating table... Attempting to create table; please wait... Sep 29, 2019 8:10:05 AM com.amazonaws.profile.path.cred.CredentialsLegacyConfigLocationProvider getLocation WARNING: Found the legacy config profiles file at [/home/ec2-user/.aws/config]. Please move it to the latest default location [~/.aws/credentials]. Successfully created table. Table status: ACTIVE Populating table... Writing data to the table... Writing 10 items for partition key: 1 Writing 10 items for partition key: 2 Writing 10 items for partition key: 3 Writing 10 items for partition key: 4 Writing 10 items for partition key: 5 Writing 10 items for partition key: 6 Writing 10 items for partition key: 7 Writing 10 items for partition key: 8 Writing 10 items for partition key: 9 Writing 10 items for partition key: 10 Running GetItem, Scan, and Query tests... First iteration of each test will result in cache misses Next iterations are cache hits GetItem test - partition key 1 and sort keys 1-10 Total time: 76.314 ms - Avg time: 7.631 ms Total time: 61.295 ms - Avg time: 6.130 ms Total time: 72.975 ms - Avg time: 7.298 ms Total time: 53.670 ms - Avg time: 5.367 ms Total time: 50.510 ms - Avg time: 5.051 ms Query test - partition key 5 and sort keys between 2 and 9 Total time: 9.622 ms - Avg time: 1.924 ms Total time: 8.949 ms - Avg time: 1.790 ms Total time: 5.223 ms - Avg time: 1.045 ms Total time: 7.567 ms - Avg time: 1.513 ms Total time: 7.285 ms - Avg time: 1.457 ms Scan test - all items in the table Total time: 28.724 ms - Avg time: 5.745 ms Total time: 19.273 ms - Avg time: 3.855 ms Total time: 14.883 ms - Avg time: 2.977 ms Total time: 16.374 ms - Avg time: 3.275 ms Total time: 18.015 ms - Avg time: 3.603 ms Attempting to delete table; please wait... Successfully deleted table.
