Revert versions of spring,servlet-api,checkstyle to compatible JDK8

Author: guohao

canteen/pom.xml

@@ -69,7 +69,7 @@
                     <dependency>
                         <groupId>com.puppycrawl.tools</groupId>
                         <artifactId>checkstyle</artifactId>
-                        <version>10.5.0</version>
+                        <version>9.3</version>
                     </dependency>
                 </dependencies>
                 <executions>

contrib/grpc-spring/pom.xml

@@ -38,9 +38,9 @@
         </dependency>
         <!-- Bring your own Spring dependency. Hence scope provided -->
         <dependency>
-            <groupId>jakarta.servlet</groupId>
-            <artifactId>jakarta.servlet-api</artifactId>
-            <version>6.0.0</version>
+            <groupId>javax.servlet</groupId>
+            <artifactId>servlet-api</artifactId>
+            <version>2.5</version>
             <scope>provided</scope>
         </dependency>
         <dependency>

contrib/pom.xml

@@ -64,7 +64,7 @@
         <slf4j.version>2.0.5</slf4j.version>
         <gson.version>2.10</gson.version> <!-- Same version as grpc-proto -->
         <mustache-java.version>0.9.10</mustache-java.version>
-        <spring.version>6.0.2</spring.version>
+        <spring.version>5.3.24</spring.version>
 
         <!-- Test Dependency Versions -->
         <junit.version>4.13.2</junit.version>
@@ -251,7 +251,7 @@
                     <dependency>
                         <groupId>com.puppycrawl.tools</groupId>
                         <artifactId>checkstyle</artifactId>
-                        <version>10.5.0</version>
+                        <version>9.3</version>
                     </dependency>
                 </dependencies>
                 <executions>

demos/grpc-java-contrib-demo/pom.xml

@@ -15,7 +15,7 @@
 
     <properties>
         <maven.deploy.skip>true</maven.deploy.skip>
-        <spring.boot.version>3.0.0</spring.boot.version>
+        <spring.boot.version>2.7.6</spring.boot.version>
     </properties>
 
     <modules>

demos/grpc-java-contrib-demo/time-service-demo/pom.xml

@@ -51,7 +51,7 @@
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-context</artifactId>
-            <version>6.0.2</version>
+            <version>5.3.24</version>
         </dependency>
         <dependency>
             <groupId>org.slf4j</groupId>
@@ -91,7 +91,7 @@
             <plugin>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-maven-plugin</artifactId>
-                <version>3.0.0</version>
+                <version>2.7.6</version>
                 <executions>
                     <execution>
                         <goals>

demos/pom.xml

@@ -64,7 +64,7 @@
         <slf4j.version>2.0.5</slf4j.version>
         <gson.version>2.10</gson.version> <!-- Same version as grpc-proto -->
         <mustache-java.version>0.9.4</mustache-java.version>
-        <spring.version>6.0.2</spring.version>
+        <spring.version>5.3.24</spring.version>
 
         <!-- Test Dependency Versions -->
         <junit.version>4.12</junit.version>
@@ -162,7 +162,7 @@
                     <dependency>
                         <groupId>com.puppycrawl.tools</groupId>
                         <artifactId>checkstyle</artifactId>
-                        <version>10.5.0</version>
+                        <version>9.3</version>
                     </dependency>
                 </dependencies>
                 <executions>

jprotoc/pom.xml

@@ -207,7 +207,7 @@
                     <dependency>
                         <groupId>com.puppycrawl.tools</groupId>
                         <artifactId>checkstyle</artifactId>
-                        <version>10.5.0</version>
+                        <version>9.3</version>
                     </dependency>
                 </dependencies>
                 <executions>