[fix](regression) use JDK 17 for Java UDF builds (#65888)

## What changed

- make `run-regression-test.sh` select and validate JDK 17 before
invoking Maven
- prefer a valid `JAVA_HOME` or `JDK_17`, with Linux and macOS discovery
fallbacks
- build the regression framework and Java UDF case jar with the same JDK
17
- compile `java-udf-src` with `maven.compiler.release=17`

## Why

The regression build depended on the caller to prepare `JAVA_HOME`, and
newer branches also switched to JDK 8 only for the Java UDF module. This
split ownership between CI and the Doris build script and could produce
incomplete case artifacts when the framework required JDK 17.

Keeping Java selection in `run-regression-test.sh` makes local and CI
builds follow the same contract and removes the Java 8-only UDF build
path.

## Validation

- `bash -n run-regression-test.sh`
- `git diff --check`
- ran `./run-regression-test.sh --clean` while the incoming `JAVA_HOME`
pointed to JDK 22; the script selected JDK 17 and Maven reported Java 17
- built `regression-test/java-udf-src` with JDK 17 successfully
- verified `Echo$EchoInt` has class major version 61 and the expected
UDF classes are present in the assembled jar

regression-test/java-udf-src/pom.xml

@@ -26,8 +26,7 @@ under the License.
     <name>Java UDF Case</name>
     <url>https://doris.apache.org/</url>
     <properties>
-        <maven.compiler.source>8</maven.compiler.source>
-        <maven.compiler.target>8</maven.compiler.target>
+        <maven.compiler.release>17</maven.compiler.release>
         <hive.version>3.1.3</hive.version>
     </properties>
 
@@ -85,10 +84,6 @@ under the License.
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.10.1</version>
-                <configuration>
-                    <source>8</source>
-                    <target>8</target>
-                </configuration>
             </plugin>
         </plugins>
     </build>

run-regression-test.sh

@@ -23,6 +23,63 @@ ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")" &>/dev/null && pwd)"
 
 DORIS_HOME="${ROOT}"
 
+java_major_version() {
+    local java_cmd="$1"
+    local spec_version
+
+    spec_version="$("${java_cmd}" -XshowSettings:properties -version 2>&1 \
+        | awk -F'= ' '/java.specification.version =/ {print $2; exit}')"
+    # Cygwin's Java properties output uses CRLF line endings.
+    spec_version="${spec_version//$'\r'/}"
+    if [[ "${spec_version}" == 1.* ]]; then
+        spec_version="${spec_version#1.}"
+    fi
+    echo "${spec_version%%.*}"
+}
+
+is_jdk17_home() {
+    local java_home="$1"
+    [[ -n "${java_home}" ]] && [[ -x "${java_home}/bin/java" ]] \
+        && [[ -x "${java_home}/bin/javac" ]] \
+        && [[ "$(java_major_version "${java_home}/bin/java")" == "17" ]]
+}
+
+find_jdk17_home() {
+    local candidate
+
+    for candidate in "${JAVA_HOME:-}" "${JDK_17:-}"; do
+        if is_jdk17_home "${candidate}"; then
+            echo "${candidate}"
+            return 0
+        fi
+    done
+
+    if [[ "$(uname -s)" == "Darwin" ]] && [[ -x /usr/libexec/java_home ]]; then
+        candidate="$(/usr/libexec/java_home -v 17 2>/dev/null || true)"
+        if is_jdk17_home "${candidate}"; then
+            echo "${candidate}"
+            return 0
+        fi
+    elif [[ -d /usr/lib/jvm ]]; then
+        while IFS= read -r candidate; do
+            if is_jdk17_home "${candidate}"; then
+                echo "${candidate}"
+                return 0
+            fi
+        done < <(find /usr/lib/jvm -mindepth 1 -maxdepth 1 \( -type d -o -type l \) 2>/dev/null | sort)
+    fi
+
+    echo "Error: JDK 17 is required. Set JAVA_HOME or JDK_17, or install JDK 17." >&2
+    return 1
+}
+
+JAVA_HOME="$(find_jdk17_home)"
+export JAVA_HOME
+export PATH="${JAVA_HOME}/bin:${PATH}"
+export JAVA="${JAVA_HOME}/bin/java"
+JAVA_MAJOR_VERSION="$(java_major_version "${JAVA}")"
+echo "Using JDK ${JAVA_MAJOR_VERSION}: ${JAVA_HOME}"
+
 # Check args
 usage() {
     echo "
@@ -227,30 +284,8 @@ if ! test -f ${RUN_JAR:+${RUN_JAR}}; then
     mkdir -p "${DORIS_HOME}"/regression-test/suites/javaudf_p0/jars
     cd "${DORIS_HOME}"/regression-test/java-udf-src || { echo "Failed to change directory to java-udf-src"; exit 1; }
 
-    # The Java UDF jar must be built with JDK 8 (source/target 8, loaded by the BE embedded
-    # JVM), while the framework above is built with the ambient JDK (>=17 in CI). Switch to a
-    # JDK 8 just for this module, falling back to the ambient JDK if none is installed
-    # (e.g. local dev boxes).
-    udf_prev_java_home="${JAVA_HOME:-}"
-    udf_jdk8_home="$(find /usr/lib/jvm -maxdepth 1 -type d -name 'java-8-*' 2>/dev/null | sed -n '1p')"
-    if [[ -n "${udf_jdk8_home}" ]]; then
-        echo "Building Java UDF with JDK 8 at ${udf_jdk8_home}"
-        export JAVA_HOME="${udf_jdk8_home}"
-    else
-        echo "WARNING: no JDK 8 found under /usr/lib/jvm; building Java UDF with ${JAVA_HOME:-the current JDK}"
-    fi
-
-    # Build UDF with retry
-    udf_build_rc=0
-    execute_maven_with_retry "${MVN_CMD} clean package -B -DskipTests=true -Dmaven.javadoc.skip=true" || udf_build_rc=1
-
-    # Restore the framework JDK regardless of the UDF build result.
-    if [[ -n "${udf_prev_java_home}" ]]; then
-        export JAVA_HOME="${udf_prev_java_home}"
-    else
-        unset JAVA_HOME
-    fi
-    if [[ "${udf_build_rc}" -ne 0 ]]; then
+    # Build the UDF test jar with the same JDK 17 used by the regression framework.
+    if ! execute_maven_with_retry "${MVN_CMD} clean package -B -DskipTests=true -Dmaven.javadoc.skip=true"; then
         echo "Failed to build UDF package"
         exit 1
     fi
@@ -264,22 +299,6 @@ if ! test -f ${RUN_JAR:+${RUN_JAR}}; then
     cd "${DORIS_HOME}" || { echo "Failed to return to DORIS_HOME"; exit 1; }
 fi
 
-# check java home
-if [[ -z "${JAVA_HOME}" ]]; then
-    echo "Error: JAVA_HOME is not set"
-    exit 1
-fi
-
-# check java version
-export JAVA="${JAVA_HOME}/bin/java"
-JAVA_SPEC_VERSION="$("${JAVA}" -XshowSettings:properties -version 2>&1 \
-    | awk -F'= ' '/java.specification.version =/ {print $2; exit}')"
-JAVA_MAJOR_VERSION="${JAVA_SPEC_VERSION%%.*}"
-if [[ "${JAVA_SPEC_VERSION}" == 1.* ]]; then
-    JAVA_MAJOR_VERSION="${JAVA_SPEC_VERSION#1.}"
-    JAVA_MAJOR_VERSION="${JAVA_MAJOR_VERSION%%.*}"
-fi
-
 # Arrow Flight SQL JDBC needs java.nio opened when the regression framework runs on JDK 17+.
 if [[ -n "${JAVA_MAJOR_VERSION}" ]] && [[ "${JAVA_MAJOR_VERSION}" -ge 17 ]] \
     && [[ " ${JAVA_OPTS:-} " != *"--add-opens=java.base/java.nio="* ]]; then