Important Notice - Forums is archived
To simplify things and help our users to be more productive, we have archived the current forum and focus our efforts on helping developers on Stack Overflow. You can post new questions on Stack Overflow or join our Discord channel.

Vaadin lets you build secure, UX-first PWAs entirely in Java.
Free ebook & tutorial.
Java 8 Client Compile with Lambda
I get the following compile error:
"Lambda expressions are allowed only at source level 1.8 or above"
After searching for it, i had to set the sourceLevel to 1.8
I did not find a way to set this.
Or do i miss something?
I use Vaadin 7.4.6 with all maven compile plugins
Could you elaborate a bit? Are you using Eclipse? Check the Java Build Path/Java Compiler for your project (right-click project > Properties).
I Use maven to build.
Maven Compiler is set to target/source 1.8
the vaadin-maven-plugin during compile of the client code is throwing this exception.
snipped from maven vaadin plugin is:
<plugin>
<groupId>com.vaadin</groupId>
<artifactId>vaadin-maven-plugin</artifactId>
<configuration>
<extraJvmArgs>-Xmx512M -Xss1024k</extraJvmArgs>
<!-- We are doing "inplace" but into subdir VAADIN/widgetsets. This way compatible with Vaadin eclipse plugin. -->
<webappDirectory>${basedir}/src/main/webapp/VAADIN/widgetsets</webappDirectory>
<hostedWebapp>${basedir}/src/main/webapp/VAADIN/widgetsets</hostedWebapp>
<!-- Most Vaadin apps don't need this stuff, guide that to target -->
<persistentunitcachedir>${project.build.directory}</persistentunitcachedir>
<deploy>${project.build.directory}/gwt-deploy</deploy>
<!-- Compile report is not typically needed either, saves hunreds of mb disk -->
<compileReport>false</compileReport>
<noServer>true</noServer>
<!-- Remove draftCompile when project is ready -->
<draftCompile>false</draftCompile>
<style>OBF</style>
<strict>true</strict>
<runTarget>http://localhost:8080/app</runTarget>
</configuration>
</plugin>
Hi Renier,
Unfortunately I think the current GWT compiler version does not support Java 8, so you can't use its features when writing client-side code :(
I know this is an old thread, but the issue still persists so maybe others could benefit from my findings.
Vaadin-client in version 7.7.6 depends on GWT 2.7 (2.7.0.vaadin4 actually) which does not support Java 8 but GWT 2.8 already does. Vaadin 8 will depend on GWT 2.8, but until it is released we can still tweak 7.7.6 to use GWT 2.8 on our own risk as written in this article.