Enhance open api capabilities:

1. Add get single item interface
2. Allow passing the appendNamespacePrefix flag when creating public namespaces

apollo-openapi/src/main/java/com/ctrip/framework/apollo/openapi/client/ApolloOpenApiClient.java

@@ -86,6 +86,17 @@ public class ApolloOpenApiClient {
     return namespaceService.getNamespaceLock(appId, env, clusterName, namespaceName);
   }
 
+  /**
+   * Get config
+   *
+   * @return the item or null if not exists
+   *
+   * @since 1.2.0
+   */
+  public OpenItemDTO getItem(String appId, String env, String clusterName, String namespaceName, String key) {
+    return itemService.getItem(appId, env, clusterName, namespaceName, key);
+  }
+
   /**
    * Add config
    * @return the created config

apollo-openapi/src/main/java/com/ctrip/framework/apollo/openapi/client/exception/ApolloOpenApiException.java

@@ -2,8 +2,15 @@ package com.ctrip.framework.apollo.openapi.client.exception;
 
 public class ApolloOpenApiException extends RuntimeException {
 
+  private int status;
+
   public ApolloOpenApiException(int status, String reason, String message) {
     super(String.format("Request to apollo open api failed, status code: %d, reason: %s, message: %s", status, reason,
         message));
+    this.status = status;
+  }
+
+  public int getStatus() {
+    return status;
   }
 }

apollo-openapi/src/main/java/com/ctrip/framework/apollo/openapi/client/service/ItemOpenApiService.java

 package com.ctrip.framework.apollo.openapi.client.service;
 
 import com.ctrip.framework.apollo.core.ConfigConsts;
+import com.ctrip.framework.apollo.openapi.client.exception.ApolloOpenApiException;
 import com.ctrip.framework.apollo.openapi.dto.OpenItemDTO;
 import com.google.common.base.Strings;
 import com.google.gson.Gson;
@@ -14,6 +15,34 @@ public class ItemOpenApiService extends AbstractOpenApiService {
     super(client, baseUrl, gson);
   }
 
+  public OpenItemDTO getItem(String appId, String env, String clusterName, String namespaceName, String key) {
+    if (Strings.isNullOrEmpty(clusterName)) {
+      clusterName = ConfigConsts.CLUSTER_NAME_DEFAULT;
+    }
+    if (Strings.isNullOrEmpty(namespaceName)) {
+      namespaceName = ConfigConsts.NAMESPACE_APPLICATION;
+    }
+
+    checkNotEmpty(appId, "App id");
+    checkNotEmpty(env, "Env");
+    checkNotEmpty(key, "Item key");
+
+    String path = String.format("envs/%s/apps/%s/clusters/%s/namespaces/%s/items/%s",
+        escapePath(env), escapePath(appId), escapePath(clusterName), escapePath(namespaceName), escapePath(key));
+
+    try (CloseableHttpResponse response = get(path)) {
+      return gson.fromJson(EntityUtils.toString(response.getEntity()), OpenItemDTO.class);
+    } catch (Throwable ex) {
+      // return null if item doesn't exist
+      if (ex instanceof ApolloOpenApiException && ((ApolloOpenApiException)ex).getStatus() == 404) {
+        return null;
+      }
+      throw new RuntimeException(String
+          .format("Get item: %s for appId: %s, cluster: %s, namespace: %s in env: %s failed", key, appId, clusterName,
+              namespaceName, env), ex);
+    }
+  }
+
   public OpenItemDTO createItem(String appId, String env, String clusterName, String namespaceName, OpenItemDTO itemDTO) {
     if (Strings.isNullOrEmpty(clusterName)) {
       clusterName = ConfigConsts.CLUSTER_NAME_DEFAULT;

apollo-openapi/src/main/java/com/ctrip/framework/apollo/openapi/dto/OpenAppNamespaceDTO.java

@@ -10,6 +10,9 @@ public class OpenAppNamespaceDTO extends BaseDTO {
 
     private boolean isPublic;
 
+    // whether to append namespace prefix for public namespace name
+    private boolean appendNamespacePrefix = true;
+
     private String comment;
 
     public String getName() {
@@ -44,6 +47,14 @@ public class OpenAppNamespaceDTO extends BaseDTO {
         isPublic = aPublic;
     }
 
+    public boolean isAppendNamespacePrefix() {
+        return appendNamespacePrefix;
+    }
+
+    public void setAppendNamespacePrefix(boolean appendNamespacePrefix) {
+        this.appendNamespacePrefix = appendNamespacePrefix;
+    }
+
     public String getComment() {
         return comment;
     }

apollo-openapi/src/test/java/com/ctrip/framework/apollo/openapi/client/service/ItemOpenApiServiceTest.java

 package com.ctrip.framework.apollo.openapi.client.service;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 import com.ctrip.framework.apollo.openapi.dto.OpenItemDTO;
 import org.apache.http.client.methods.HttpDelete;
+import org.apache.http.client.methods.HttpGet;
 import org.apache.http.client.methods.HttpPost;
 import org.apache.http.client.methods.HttpPut;
 import org.apache.http.entity.ContentType;
@@ -40,6 +42,32 @@ public class ItemOpenApiServiceTest extends AbstractOpenApiServiceTest {
     itemOpenApiService = new ItemOpenApiService(httpClient, someBaseUrl, gson);
   }
 
+  @Test
+  public void testGetItem() throws Exception {
+    String someKey = "someKey";
+
+    final ArgumentCaptor<HttpGet> request = ArgumentCaptor.forClass(HttpGet.class);
+
+    itemOpenApiService.getItem(someAppId, someEnv, someCluster, someNamespace, someKey);
+
+    verify(httpClient, times(1)).execute(request.capture());
+
+    HttpGet get = request.getValue();
+
+    assertEquals(String
+        .format("%s/envs/%s/apps/%s/clusters/%s/namespaces/%s/items/%s", someBaseUrl, someEnv,
+            someAppId, someCluster, someNamespace, someKey), get.getURI().toString());
+  }
+
+  @Test
+  public void testGetNotExistedItem() throws Exception {
+    String someKey = "someKey";
+
+    when(statusLine.getStatusCode()).thenReturn(404);
+
+    assertNull(itemOpenApiService.getItem(someAppId, someEnv, someCluster, someNamespace, someKey));
+  }
+
   @Test
   public void testCreateItem() throws Exception {
     String someKey = "someKey";

apollo-portal/src/main/java/com/ctrip/framework/apollo/openapi/v1/controller/ItemController.java

@@ -33,6 +33,14 @@ public class ItemController {
   @Autowired
   private UserService userService;
 
+  @RequestMapping(value = "/apps/{appId}/clusters/{clusterName}/namespaces/{namespaceName}/items/{key:.+}", method = RequestMethod.GET)
+  public OpenItemDTO getItem(@PathVariable String appId, @PathVariable String env, @PathVariable String clusterName,
+      @PathVariable String namespaceName, @PathVariable String key) {
+
+    ItemDTO itemDTO = itemService.loadItem(Env.fromString(env), appId, clusterName, namespaceName, key);
+
+    return itemDTO == null ? null : OpenApiBeanUtils.transformFromItemDTO(itemDTO);
+  }
 
   @PreAuthorize(value = "@consumerPermissionValidator.hasModifyNamespacePermission(#request, #appId, #namespaceName, #env)")
   @RequestMapping(value = "/apps/{appId}/clusters/{clusterName}/namespaces/{namespaceName}/items", method = RequestMethod.POST)

apollo-portal/src/main/java/com/ctrip/framework/apollo/openapi/v1/controller/NamespaceController.java

@@ -77,7 +77,7 @@ public class NamespaceController {
     }
 
     AppNamespace appNamespace = OpenApiBeanUtils.transformToAppNamespace(appNamespaceDTO);
-    AppNamespace createdAppNamespace = appNamespaceService.createAppNamespaceInLocal(appNamespace);
+    AppNamespace createdAppNamespace = appNamespaceService.createAppNamespaceInLocal(appNamespace, appNamespaceDTO.isAppendNamespacePrefix());
 
     publisher.publishEvent(new AppNamespaceCreationEvent(createdAppNamespace));