[AMORO-3531] Drop support for java8

.github/workflows/core-hadoop2-ci.yml

@@ -37,7 +37,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        jdk: [ '8', '11' ]
+        jdk: [ '11' ]
     name: Build Amoro with JDK ${{ matrix.jdk }}
     steps:
       - uses: actions/checkout@v3

.github/workflows/core-hadoop3-ci.yml

@@ -37,7 +37,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        jdk: [ '8', '11' ]
+        jdk: [ '11' ]
         spark: [ '3.3', '3.5' ]
     name: Build Amoro with JDK ${{ matrix.jdk }} Spark-${{ matrix.spark }}
     steps:

CONTRIBUTING.md

@@ -92,7 +92,7 @@ for reference.
 The following guide describes how to import the Amoro project into IntelliJ IDEA and deploy it.
 
 ### Requirements
-+ Java Version: Java 8 or Java 11 is required.
++ Java Version: Java 11 is required.
 
 #### Required plugins
 1. Go to `Settings` → `Plugins` in IntelliJ IDEA.

docker/optimizer-flink/Dockerfile

@@ -14,7 +14,7 @@
 #  See the License for the specific language governing permissions and
 # limitations under the License.
 
-ARG FLINK_VERSION=1.20.0-java8
+ARG FLINK_VERSION=1.20.0-java11
 
 FROM flink:${FLINK_VERSION}
 

docs/admin-guides/deployment.md

@@ -30,7 +30,7 @@ You can choose to download the stable release package from [download page](../..
 
 ## System requirements
 
-- Java 8 is required.
+- Java 11 is required.
 - Optional: A RDBMS (PostgreSQL 14.x or higher, MySQL 5.5 or higher)
 - Optional: ZooKeeper 3.4.x or higher
 

pom.xml

@@ -1458,13 +1458,6 @@
             </properties>
         </profile>
 
-        <profile>
-            <id>java8</id>
-            <properties>
-                <java.target.version>8</java.target.version>
-                <java.source.version>8</java.source.version>
-            </properties>
-        </profile>
         <profile>
             <id>java11</id>
             <activation>