update CRD generation guides

Update docs/generate-model-from-third-party-resources.md

Co-authored-by: Erik Godding Boye <[email protected]>

Update docs/generate-model-from-third-party-resources.md

Co-authored-by: Erik Godding Boye <[email protected]>

fold -c flag explaination

Author: yue9944882

docs/generate-model-from-third-party-resources.md

@@ -8,6 +8,20 @@ and try to program java to operate the extended APIs. The generation process req
 
 ### Steps
 
+##### Download and checkout generator scripts
+
+Download the scripts for code generation then checkout to the correct directory:
+
+```
+git clone https://github.com/kubernetes-client/gen
+cd gen/openapi/
+```
+
+And also the code generation requires accessing docker service on the host:
+
+```
+docker ps
+```
 
 ##### Fetch openapi spec from the cluster
 
@@ -23,26 +37,31 @@ don't forget to deploy your CRDs into the local-run kubernetes cluster.
 
 ##### Generate Java model from the downloaded openapi spec
 
-Run the following command and there will be a java sources generated under `/tmp/java`. 
+Run the following commands and there will be a java sources generated under `/tmp/java`. 
 
 ```
-docker run -i --rm yue9944882/java-model-gen < /tmp/swagger | tar -xzf - -C /tmp/
+bash java-crd-cmd.sh -o /tmp/java  < /tmp/swagger 
 ```
 
-By default, the package-name of generated codes will be `io.kubernetes.client`. If you want to override the package-name, consider 
+By default, the package name of generated java classes will be `io.kubernetes.client`. If you want to override the package name, consider 
 use `-p <package_name>` flag. Additionally, you can use `-l <length>` option to make the generator to trim the length of generated 
 class name, the lower number generates shorter names. e.g. for a CRD named `crontabs.v1.example.io`, with `-l 1` the generated 
-name will be `CronTab`, otherwise with `-l3` it will be `ExampleV1Crontab`.
+name will be `CronTab`, otherwise with `-l3` it will be `ExampleV1Crontab`. And also if you feel like only generating classes for a few CRDs
+instead of the whole lump of downloaded openapi specs, please use `-n` to filter out your target CRDs. For all supported flags, use `-h` 
+for help info as is shown in the following:
 
 ```
-docker run -i --rm yue9944882/java-model-gen -p com.example < /tmp/swagger | tar -xzf - -C /tmp/
+Usage: generate a java project using input openapi spec from stdin
+ -n: the prefix of the target CRD's api group to generate.
+ -p: the base package name of the generated java project. 
+ -o: output directory of the generated java project. 
+ -l: keep the n last segments for the generated class name. 
 ```
 
-
 ##### Best practice to manipulate Java models?
 
 It's recommended to use [CustomObjectApi](https://github.com/kubernetes-client/java/blob/master/kubernetes/src/main/java/io/kubernetes/client/apis/CustomObjectsApi.java)
-to read/write the extended resources from/to the cluster.
+or [GenericKubernetesApi](https://github.com/kubernetes-client/java/blob/master/extended/src/main/java/io/kubernetes/client/extended/generic/GenericKubernetesApi.java) to read/write the extended resources from/to the cluster.
 
 ### Hand-on exercise
 
@@ -106,23 +125,23 @@ kubectl get --raw="/openapi/v2" > /tmp/swagger
 3. Generate models under `/tmp/java` directory
 
 ```bash
-docker run -i --rm yue9944882/java-model-gen -p com.example < /tmp/swagger | tar -xzf - -C /tmp/
+bash java-crd-cmd.sh -n com.example -p com.example -l 2 -o /tmp/java < /tmp/swagger
 ```
 
 after generation you will see bunch of generated model sources under the `/tmp/java`: 
 
 ```bash
-ls -R /tmp/java/ | grep ComExample
-ComExampleStableV1CronTab.java
-ComExampleStableV1CronTabList.java
-ComExampleStableV1CronTabSpec.java
+ls -R /tmp/java/ | grep V1CronTab
+V1CronTab.java
+V1CronTabList.java
+V1CronTabSpec.java
 ```
 
 you're now free to request the models from master apiserver now:
 
 ```java
 // request extended models
-ComExampleStableV1CronTab crontab = new ComExampleStableV1CronTab();
+V1CronTab crontab = new V1CronTab();
 CustomObjectsApi customObjectsApi = new CustomObjectsApi(apiClient);
 customObjectsApi.createNamespacedCustomObject(
         "com.example.stable",
@@ -132,10 +151,13 @@ customObjectsApi.createNamespacedCustomObject(
         crontab,
         "true"
 );
+
+// alternatively use generic kubernetes api 
+GenericKubernetesApi<V1CronTab, V1CronTabList> crontabClient =
+    new GenericKubernetesApi<>(V1CronTab.class, V1CronTabList.class, "com.example.stable", "v1", "crontabs", apiClient);
+KubernetesApiResponse<V1CronTab> createResponse = crontabClient.create(crontab);
 ```
 
 
 
 
-
-