Eclipse Buildpath issue for after Maven : Update Project

Question

We are working on Sprint Boot in eclipse IDE Oxygen 4.7.3a with RTC Client v6.0.5

RTC - code repository where we keep our code base

The problem is whenever we do Right click Project > Maven > Update Project (Force Update of Snapshots/Releases)

JRE System Library is downgraded to J2SE-1.5 from Workspace default JRE (java-11-openjdk)

It makes us to fix Java build path again to openjdk-11 manually. How can we avoid auto JRE downgrade after Maven > Update Project

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.6</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.xx.rt.edgeservice.discoveryserver</groupId>
    <artifactId>rt-edge-service-discovery</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>rt-edge-service-discovery</name>
    <description>XX Service Discovery</description>
    <properties>
        <java.version>11</java.version>
        <spring-cloud.version>2020.0.4</spring-cloud.version>
        <jacoco.version>0.8.6</jacoco.version>
        <sonar.java.coveragePlugin>jacoco</sonar.java.coveragePlugin>
        <sonar.dynamicAnalysis>reuseReports</sonar.dynamicAnalysis>
        <sonar.jacoco.reportPath>${project.basedir}/../target/jacoco.exec</sonar.jacoco.reportPath>
        <sonar.language>java</sonar.language>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.sonarsource.scanner.maven</groupId>
                <artifactId>sonar-maven-plugin</artifactId>
                <version>3.4.0.905</version>
            </plugin>
            <plugin>
                <groupId>org.jacoco</groupId>
                <artifactId>jacoco-maven-plugin</artifactId>
                <version>${jacoco.version}</version>
                <executions>
                    <execution>
                        <id>jacoco-initialize</id>
                        <goals>
                            <goal>prepare-agent</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>jacoco-site</id>
                        <phase>package</phase>
                        <goals>
                            <goal>report</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>

</project>

Answer 1

For Simple Maven Project

M2Eclipse is using target parameter from maven-compiler-plugin information to set your eclipse project.

The default value is 1.5, if you are using a maven version under 3.8.0.

So you need to configure at maven level which java version you want to target by changing your pom.xml with :

  <build>
    <plugins>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.10.1</version>
        <configuration>
          <source>11</source>
          <target>11</target>
        </configuration>
      </plugin>
    </plugins>
  </build>

OR

<properties>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
</properties>

About java version number, I think those both syntax (1.x and x) are supported. (E.g. for java8, 1.8 or 8)

For Sping Boot

It should work to use :

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>version (e.g 2.5.6)</version>
</parent>
<properties>
    <java.version>11</java.version>
</properties>

If you look at spring-boot-starter-parent, you will see that java.version properties is used to set maven.compiler.source and maven.compiler.target