Add okhttp4-gson codegen

Add support for okhttp4-gson as a replacement for okhttp-gson

okhttp-gson is based on okhttp 2.x which is no longer supported. okhttp 3.x is also [not supported anymore](https://square.github.io/okhttp/security/security/)

Creating a new target for codegen since okhttp 4.x is a breaking change over the okhttp 2.x with the changed package names.

The overall change is similar to the existing code with a few updates
- updates due to deprecations documented in https://square.github.io/okhttp/changelogs/changelog_3x/#version-300-rc1
- kept the utility methods in the existing code as-is

tested `mvn package`, ran the petstore generation scripts and the integration tests that are generated

Fixes #9606

Author: deepsan

Diff for: bin/java-petstore-all.sh

@@ -6,6 +6,8 @@
 ./bin/java-petstore-feign.sh
 ./bin/java-petstore-okhttp-gson.sh
 ./bin/java-petstore-okhttp-gson-parcelable.sh
+./bin/java-petstore-okhttp4-gson.sh
+./bin/java-petstore-okhttp4-gson-parcelable.sh
 ./bin/java-petstore-retrofit.sh
 ./bin/java-petstore-retrofit2.sh
 ./bin/java-petstore-retrofit2rx.sh

Diff for: bin/java-petstore-okhttp4-gson-parcelable.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+
+SCRIPT="$0"
+
+while [ -h "$SCRIPT" ] ; do
+  ls=`ls -ld "$SCRIPT"`
+  link=`expr "$ls" : '.*-> \(.*\)$'`
+  if expr "$link" : '/.*' > /dev/null; then
+    SCRIPT="$link"
+  else
+    SCRIPT=`dirname "$SCRIPT"`/"$link"
+  fi
+done
+
+if [ ! -d "${APP_DIR}" ]; then
+  APP_DIR=`dirname "$SCRIPT"`/..
+  APP_DIR=`cd "${APP_DIR}"; pwd`
+fi
+
+executable="./modules/swagger-codegen-cli/target/swagger-codegen-cli.jar"
+
+if [ ! -f "$executable" ]
+then
+  mvn clean package
+fi
+
+# if you've executed sbt assembly previously it will use that instead.
+export JAVA_OPTS="${JAVA_OPTS} -XX:MaxPermSize=256M -Xmx1024M -DloggerPath=conf/log4j.properties"
+ags="$@ generate -t modules/swagger-codegen/src/main/resources/Java/libraries/okhttp4-gson -i modules/swagger-codegen/src/test/resources/2_0/petstore-with-fake-endpoints-models-for-testing.yaml -l java -c bin/java-petstore-okhttp4-gson.json -o samples/client/petstore/java/okhttp4-gson-parcelableModel -DhideGenerationTimestamp=true,parcelableModel=true"
+
+rm -rf samples/client/petstore/java/okhttp4-gson-parcelableModel/src/main
+find samples/client/petstore/java/okhttp4-gson-parcelableModel -maxdepth 1 -type f ! -name "README.md" -exec rm {} +
+java $JAVA_OPTS -jar $executable $ags

Diff for: bin/java-petstore-okhttp4-gson.json

@@ -0,0 +1,4 @@
+{
+    "library": "okhttp4-gson",
+    "artifactId": "swagger-petstore-okhttp4-gson"
+}

Diff for: bin/java-petstore-okhttp4-gson.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+
+SCRIPT="$0"
+
+while [ -h "$SCRIPT" ] ; do
+  ls=`ls -ld "$SCRIPT"`
+  link=`expr "$ls" : '.*-> \(.*\)$'`
+  if expr "$link" : '/.*' > /dev/null; then
+    SCRIPT="$link"
+  else
+    SCRIPT=`dirname "$SCRIPT"`/"$link"
+  fi
+done
+
+if [ ! -d "${APP_DIR}" ]; then
+  APP_DIR=`dirname "$SCRIPT"`/..
+  APP_DIR=`cd "${APP_DIR}"; pwd`
+fi
+
+executable="./modules/swagger-codegen-cli/target/swagger-codegen-cli.jar"
+
+if [ ! -f "$executable" ]
+then
+  mvn clean package
+fi
+
+# if you've executed sbt assembly previously it will use that instead.
+export JAVA_OPTS="${JAVA_OPTS} -XX:MaxPermSize=256M -Xmx1024M -DloggerPath=conf/log4j.properties"
+ags="$@ generate -t modules/swagger-codegen/src/main/resources/Java/libraries/okhttp4-gson -i modules/swagger-codegen/src/test/resources/2_0/petstore-with-fake-endpoints-models-for-testing.yaml -l java -c bin/java-petstore-okhttp4-gson.json -o samples/client/petstore/java/okhttp4-gson -DhideGenerationTimestamp=true"
+
+rm -rf samples/client/petstore/java/okhttp4-gson/src/main
+find samples/client/petstore/java/okhttp4-gson -maxdepth 1 -type f ! -name "README.md" -exec rm {} +
+java $JAVA_OPTS -jar $executable $ags

Diff for: bin/security/java-petstore-okhttp4-gson.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+
+SCRIPT="$0"
+
+while [ -h "$SCRIPT" ] ; do
+  ls=`ls -ld "$SCRIPT"`
+  link=`expr "$ls" : '.*-> \(.*\)$'`
+  if expr "$link" : '/.*' > /dev/null; then
+    SCRIPT="$link"
+  else
+    SCRIPT=`dirname "$SCRIPT"`/"$link"
+  fi
+done
+
+if [ ! -d "${APP_DIR}" ]; then
+  APP_DIR=`dirname "$SCRIPT"`/..
+  APP_DIR=`cd "${APP_DIR}"; pwd`
+fi
+
+executable="./modules/swagger-codegen-cli/target/swagger-codegen-cli.jar"
+
+if [ ! -f "$executable" ]
+then
+  mvn clean package
+fi
+
+# if you've executed sbt assembly previously it will use that instead.
+export JAVA_OPTS="${JAVA_OPTS} -XX:MaxPermSize=256M -Xmx1024M -DloggerPath=conf/log4j.properties"
+ags="$@ generate -t modules/swagger-codegen/src/main/resources/Java/libraries/okhttp4-gson -i modules/swagger-codegen/src/test/resources/2_0/petstore-security-test.yaml -l java -c bin/java-petstore-okhttp4-gson.json -o samples/client/petstore-security-test/java/okhttp4-gson -DhideGenerationTimestamp=true"
+
+rm -rf samples/client/petstore-security-test/java/okhttp4-gson/src/main
+find samples/client/petstore-security-test/java/okhttp4-gson -maxdepth 1 -type f ! -name "README.md" -exec rm {} +
+java $JAVA_OPTS -jar $executable $ags

Diff for: modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/JavaClientCodegen.java

@@ -71,7 +71,7 @@ public JavaClientCodegen() {
 
         cliOptions.add(CliOption.newBoolean(USE_RX_JAVA, "Whether to use the RxJava adapter with the retrofit2 library."));
         cliOptions.add(CliOption.newBoolean(USE_RX_JAVA2, "Whether to use the RxJava2 adapter with the retrofit2 library."));
-        cliOptions.add(CliOption.newBoolean(PARCELABLE_MODEL, "Whether to generate models for Android that implement Parcelable with the okhttp-gson library."));
+        cliOptions.add(CliOption.newBoolean(PARCELABLE_MODEL, "Whether to generate models for Android that implement Parcelable with the okhttp-gson or okhttp4-gson library."));
         cliOptions.add(CliOption.newBoolean(USE_PLAY_WS, "Use Play! Async HTTP client (Play WS API)"));
         cliOptions.add(CliOption.newString(PLAY_VERSION, "Version of Play! Framework (possible values \"play24\", \"play25\")"));
         cliOptions.add(CliOption.newBoolean(USE_BEANVALIDATION, "Use BeanValidation API annotations"));
@@ -85,6 +85,7 @@ public JavaClientCodegen() {
         supportedLibraries.put("feign", "HTTP client: OpenFeign 9.4.0. JSON processing: Jackson 2.11.4");
         supportedLibraries.put("jersey2", "HTTP client: Jersey client 2.29.1. JSON processing: Jackson 2.11.4");
         supportedLibraries.put("okhttp-gson", "HTTP client: OkHttp 2.7.5. JSON processing: Gson 2.8.1. Enable Parcelable models on Android using '-DparcelableModel=true'. Enable gzip request encoding using '-DuseGzipFeature=true'.");
+        supportedLibraries.put("okhttp4-gson", "HTTP client: OkHttp 4.10.0. JSON processing: Gson 2.8.1. Enable Parcelable models on Android using '-DparcelableModel=true'. Enable gzip request encoding using '-DuseGzipFeature=true'.");
         supportedLibraries.put(RETROFIT_1, "HTTP client: OkHttp 2.7.5. JSON processing: Gson 2.3.1 (Retrofit 1.9.0). IMPORTANT NOTE: retrofit1.x is no longer actively maintained so please upgrade to 'retrofit2' instead.");
         supportedLibraries.put(RETROFIT_2, "HTTP client: OkHttp 3.8.0. JSON processing: Gson 2.6.1 (Retrofit 2.3.0). Enable the RxJava adapter using '-DuseRxJava[2]=true'. (RxJava 1.x or 2.x)");
         supportedLibraries.put("resttemplate", "HTTP client: Spring RestTemplate 4.3.9-RELEASE. JSON processing: Jackson 2.11.4");
@@ -235,8 +236,8 @@ public void processOpts() {
             additionalProperties.put("jackson", "true");
             supportingFiles.add(new SupportingFile("ParamExpander.mustache", invokerFolder, "ParamExpander.java"));
             supportingFiles.add(new SupportingFile("EncodingUtils.mustache", invokerFolder, "EncodingUtils.java"));
-        } else if ("okhttp-gson".equals(getLibrary()) || StringUtils.isEmpty(getLibrary())) {
-            // the "okhttp-gson" library template requires "ApiCallback.mustache" for async call
+        } else if ("okhttp-gson".equals(getLibrary()) || "okhttp4-gson".equals(getLibrary()) || StringUtils.isEmpty(getLibrary())) {
+            // the "okhttp-gson" and "okhttp4-gson" library template requires "ApiCallback.mustache" for async call
             supportingFiles.add(new SupportingFile("ApiCallback.mustache", invokerFolder, "ApiCallback.java"));
             supportingFiles.add(new SupportingFile("ApiResponse.mustache", invokerFolder, "ApiResponse.java"));
             supportingFiles.add(new SupportingFile("JSON.mustache", invokerFolder, "JSON.java"));

Diff for: modules/swagger-codegen/src/main/resources/Java/libraries/okhttp4-gson/ApiCallback.mustache

@@ -0,0 +1,51 @@
+{{>licenseInfo}}
+
+package {{invokerPackage}};
+
+import java.io.IOException;
+
+import java.util.Map;
+import java.util.List;
+
+/**
+ * Callback for asynchronous API call.
+ *
+ * @param <T> The return type
+ */
+public interface ApiCallback<T> {
+    /**
+     * This is called when the API call fails.
+     *
+     * @param e The exception causing the failure
+     * @param statusCode Status code of the response if available, otherwise it would be 0
+     * @param responseHeaders Headers of the response if available, otherwise it would be null
+     */
+    void onFailure(ApiException e, int statusCode, Map<String, List<String>> responseHeaders);
+
+    /**
+     * This is called when the API call succeeded.
+     *
+     * @param result The result deserialized from response
+     * @param statusCode Status code of the response
+     * @param responseHeaders Headers of the response
+     */
+    void onSuccess(T result, int statusCode, Map<String, List<String>> responseHeaders);
+
+    /**
+     * This is called when the API upload processing.
+     *
+     * @param bytesWritten bytes Written
+     * @param contentLength content length of request body
+     * @param done write end
+     */
+    void onUploadProgress(long bytesWritten, long contentLength, boolean done);
+
+    /**
+     * This is called when the API downlond processing.
+     *
+     * @param bytesRead bytes Read
+     * @param contentLength content lenngth of the response
+     * @param done Read end
+     */
+    void onDownloadProgress(long bytesRead, long contentLength, boolean done);
+}