update build.gradle to work with gradle 7.x, add test (#10669)

samples/client/petstore/java/okhttp-gson-dynamicOperations/build.gradle

@@ -7,8 +7,7 @@ version = '1.0.0'
 
 buildscript {
     repositories {
-        maven { url "https://repo1.maven.org/maven2" }
-        jcenter()
+        mavenCentral()
     }
     dependencies {
         classpath 'com.android.tools.build:gradle:2.3.+'
@@ -17,7 +16,7 @@ buildscript {
 }
 
 repositories {
-    jcenter()
+    mavenCentral()
 }
 sourceSets {
     main.java.srcDirs = ['src/main/java']
@@ -80,14 +79,17 @@ if(hasProperty('target') && target == 'android') {
 } else {
 
     apply plugin: 'java'
-    apply plugin: 'maven'
+    apply plugin: 'maven-publish'
 
     sourceCompatibility = JavaVersion.VERSION_1_8
     targetCompatibility = JavaVersion.VERSION_1_8
 
-    install {
-        repositories.mavenInstaller {
-            pom.artifactId = 'petstore-okhttp-gson-dynamicoperations'
+    publishing {
+        publications {
+            maven(MavenPublication) {
+               artifactId = 'petstore-okhttp-gson-dynamicoperations'
+               from components.java
+            }
         }
     }
 
@@ -115,6 +117,7 @@ dependencies {
     implementation 'io.swagger.parser.v3:swagger-parser-v3:2.0.23'
     implementation "jakarta.annotation:jakarta.annotation-api:$jakarta_annotation_version"
     testImplementation 'junit:junit:4.13.1'
+    testImplementation 'org.mockito:mockito-core:3.11.2'
 }
 
 javadoc {