CODEWITHSUNDEEP
javamavenjava-8compilation
david.t_92
david.t_92

Reputation: 2051

Maven compilation error try-with-resources

I have the following configuration in my system:

Apache Maven 3.5.2 Maven home: /usr/share/maven Java version: 1.8.0_162, vendor: Oracle Corporation Java home: /usr/lib/jvm/java-8-openjdk-amd64/jre Default locale: en_US, platform encoding: UTF-8 OS name: "linux", version: "4.15.0-20-generic", arch: "amd64", family: "unix"

When I compile (using maven) my project that have Try-with-Resources I get the following error:

/path/driver.java:[29,13] try-with-resources is not supported in -source 1.5
[ERROR]   (use -source 7 or higher to enable try-with-resources)

I have tryed to add the flag -source 7 but thats not the way to solve the problem cause it give me this other error:

[ERROR] Error executing Maven.
[ERROR] The specified user settings file does not exist: /path/ource

I have search in internet for the first error and I didn't found anything

Upvotes: 1

Views: 545

Answers (3)

Ravindra Ranwala
Ravindra Ranwala

Reputation: 21124

If you want to use the Java 8 language features (-source 1.8) and also want the compiled classes to be compatible with JVM 1.8 (-target 1.8), you can either add the two following properties, which are the default property names for the plugin parameters:

<project>
  [...]
  <properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>
  [...]
</project>

or configure the plugin directly:

<project>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.7.0</version>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

Check out this article for further details. However try-with-resources was introduced in JDK 1.7 (internal) version.

Upvotes: 3

Hemant Patel
Hemant Patel

Reputation: 3260

One option already suggested by @Ravindra. Another option is to add properties.

<properties>
  <maven.compiler.source>1.8</maven.compiler.source>
  <maven.compiler.target>1.8</maven.compiler.target>
</properties>

See maven-compiler-plugin refeerence.

Upvotes: 1

Rajan Desai
Rajan Desai

Reputation: 79

To answer the first part, add the following lines to the POM to set language level

<properties>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
</properties>

After adding those lines you can successfully build your jar, although when you run it your jar will give a no main manifest attribute error.

This can either be fixed by running like java -cp app.jar com.somepackage.SomeClass

or to correct this and make an executable jar, make your pom look like

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <executions>
                <execution>
                    <id>copy-dependencies</id>
                    <phase>prepare-package</phase>
                    <goals>
                        <goal>copy-dependencies</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${project.build.directory}/lib</outputDirectory>
                        <overWriteReleases>false</overWriteReleases>
                        <overWriteSnapshots>false</overWriteSnapshots>
                        <overWriteIfNewer>true</overWriteIfNewer>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <classpathPrefix>lib/</classpathPrefix>
                        <mainClass>fully.qualified.main</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
    </plugins>
</build>

Upvotes: 1

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