Adding pagination utility

examples/src/main/java/io/kubernetes/client/examples/PagerExample.java

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+/*
+Copyright 2019 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+ */
+package io.kubernetes.client.examples;
+
+import io.kubernetes.client.ApiClient;
+import io.kubernetes.client.Configuration;
+import io.kubernetes.client.apis.CoreV1Api;
+import io.kubernetes.client.models.V1Namespace;
+import io.kubernetes.client.models.V1NamespaceList;
+import io.kubernetes.client.pager.Pager;
+import io.kubernetes.client.pager.PagerParams;
+import io.kubernetes.client.util.Config;
+import java.io.IOException;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * A simple example of how to use the Java API
+ *
+ * <p>Easiest way to run this: mvn exec:java
+ * -Dexec.mainClass="io.kubernetes.client.examples.PagerExample"
+ *
+ * <p>From inside $REPO_DIR/examples
+ */
+public class PagerExample {
+  public static void main(String[] args) throws IOException {
+
+    ApiClient client = Config.defaultClient();
+    client.getHttpClient().setReadTimeout(60, TimeUnit.SECONDS);
+    Configuration.setDefaultApiClient(client);
+    CoreV1Api api = new CoreV1Api();
+    int i = 0;
+    Pager pager =
+        new Pager<V1Namespace, V1NamespaceList>(
+            (PagerParams param) -> {
+              try {
+                return api.listNamespaceCall(
+                    null,
+                    null,
+                    param.getContinue(),
+                    null,
+                    null,
+                    param.getLimit(),
+                    null,
+                    1,
+                    null,
+                    null,
+                    null);
+              } catch (Exception e) {
+                throw new RuntimeException(e);
+              }
+            },
+            client,
+            10,
+            V1NamespaceList.class);
+    while (pager.hasNext()) {
+      V1NamespaceList list = (V1NamespaceList) pager.next();
+      List<V1Namespace> items = list.getItems();
+      System.out.println("count:" + items.size());
+      for (V1Namespace namespace : items) {
+        System.out.println(namespace.getMetadata().getName());
+      }
+      System.out.println("------------------" + (++i));
+    }
+  }
+}

util/src/main/java/io/kubernetes/client/pager/Pager.java

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+/*
+Copyright 2019 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+ */
+package io.kubernetes.client.pager;
+
+import com.squareup.okhttp.Call;
+import io.kubernetes.client.ApiClient;
+import io.kubernetes.client.ApiException;
+import io.kubernetes.client.models.V1ListMeta;
+import io.kubernetes.client.util.Reflect;
+import io.kubernetes.client.util.exception.ObjectMetaReflectException;
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.util.function.Function;
+
+public class Pager<ApiType, ApiListType> {
+  private String continueToken;
+  private Integer limit;
+  private ApiClient client;
+  private Call call;
+  private Type listType;
+  private Function<PagerParams, Call> listFunc;
+
+  /**
+   * Pagination in kubernetes list call depends on continue and limit variable
+   *
+   * @param listFunc lambda of type: (PagerParams p)->{return
+   *     list<*>[namespace[s|d]]*<*>Call(...p.getContinue(),...p.getLimit()...);}
+   * @param client instance of {@link ApiClient}
+   * @param limit size of list to be fetched
+   * @param listType Type of list to be fetched
+   */
+  public Pager(
+      Function<PagerParams, Call> listFunc, ApiClient client, Integer limit, Type listType) {
+    this.listFunc = listFunc;
+    this.client = client;
+    this.limit = limit;
+    this.listType = listType;
+  }
+
+  /**
+   * returns false if kubernetes server has exhausted List.
+   *
+   * @return
+   */
+  public Boolean hasNext() {
+    if (continueToken == null && call != null) {
+      return Boolean.FALSE;
+    }
+    return Boolean.TRUE;
+  }
+
+  /**
+   * returns next chunk of List. size of list depends on limit set in constructor.
+   *
+   * @return Object
+   */
+  public <ApiType> ApiListType next() {
+    return next(null);
+  }
+
+  /**
+   * returns next chunk of list. size of list depends on limit set in constructor or nextLimit.
+   *
+   * @param nextLimit
+   * @return
+   */
+  public <ApiType> ApiListType next(Integer nextLimit) {
+    try {
+      call = getNextCall(nextLimit);
+      return executeRequest(call);
+    } catch (Exception e) {
+      if (e instanceof ApiException) {
+        throw new RuntimeException(((ApiException) e).getResponseBody());
+      }
+      throw new RuntimeException(e);
+    }
+  }
+
+  /** returns next list call by setting continue variable and limit */
+  private Call getNextCall(Integer nextLimit) {
+    PagerParams params = new PagerParams((nextLimit != null) ? nextLimit : limit);
+    if (continueToken != null) {
+      params.setContinue(continueToken);
+    }
+    return listFunc.apply(params);
+  }
+
+  /** executes the list call and sets the continue variable for next list call */
+  private <ApiType> ApiListType executeRequest(Call call)
+      throws IOException, ApiException, ObjectMetaReflectException {
+    ApiListType data = client.handleResponse(call.execute(), listType);
+    V1ListMeta listMetaData = Reflect.listMetadata(data);
+    continueToken = listMetaData.getContinue();
+    return data;
+  }
+}

util/src/main/java/io/kubernetes/client/pager/PagerParams.java

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+/*
+Copyright 2019 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+ */
+package io.kubernetes.client.pager;
+
+public class PagerParams {
+
+  private Integer limit;
+  private String continueToken;
+
+  public PagerParams(Integer limit) {
+    this.limit = limit;
+  }
+
+  public PagerParams(Integer limit, String continueToken) {
+    this.limit = limit;
+    this.continueToken = continueToken;
+  }
+
+  public Integer getLimit() {
+    return limit;
+  }
+
+  public String getContinue() {
+    return continueToken;
+  }
+
+  public void setContinue(String continueToken) {
+    this.continueToken = continueToken;
+  }
+}