Java ODataSerializer.entityCollection方法代码示例

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
@Override
public void readEntityCollection(
    ODataRequest request,
    ODataResponse response,
    UriInfo uriInfo,
    ContentType responseFormat) throws ODataApplicationException, ODataLibraryException {

  // First path segment is Entity Set.
  List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
  UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0);
  EdmEntitySet entitySet = uriResourceEntitySet.getEntitySet();

  // Retrieve entities from backend.
  EntityCollection entityCollection = entityRepository.list(entitySet, uriInfo);

  // Serialize to response format.
  ContextURL contextUrl = ContextURL.with()
      .entitySet(entitySet)
      .build();
  EntityCollectionSerializerOptions options = EntityCollectionSerializerOptions.with()
      .id(request.getRawBaseUri() + "/" + entitySet.getName())
      .contextURL(contextUrl)
      .build();
  ODataSerializer serializer = odata.createSerializer(responseFormat);
  SerializerResult serializerResult = serializer.entityCollection(
      serviceMetadata, entitySet.getEntityType(), entityCollection, options);

  // Set response attributes.
  response.setContent(serializerResult.getContent());
  response.setStatusCode(HttpStatusCode.OK.getStatusCode());
  response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
@Override
protected SerializerResult serialize(ODataSerializer serializer,
        InstanceData<EdmEntityType, AbstractEntityCollection> data,
        ElasticEdmEntitySet entitySet, UriInfo uriInfo) throws SerializerException {
    String id = request.getRawBaseUri() + "/" + entitySet.getEntityType();
    ExpandOption expand = uriInfo.getExpandOption();
    SelectOption select = uriInfo.getSelectOption();
    CountOption count = uriInfo.getCountOption();
    return serializer.entityCollection(serviceMetadata, data.getType(), data.getValue(),
            EntityCollectionSerializerOptions.with()
                    .contextURL(createContextUrl(entitySet, false, expand, select, null)).id(id)
                    .count(count).select(select).expand(expand).build());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request,
		ODataResponse response, UriInfo uriInfo, ContentType responseFormat)
		throws ODataApplicationException, SerializerException {

	// 1st we have retrieve the requested EntitySet from the uriInfo object
	// (representation of the parsed service URI)
	List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
	UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths
			.get(0); // in our example, the first segment is the EntitySet
	EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

	// 2nd: fetch the data from backend for this requested EntitySetName //
	// it has to be delivered as EntitySet object
	EntitySet entitySet = getData(uriInfo);

	// 3rd: create a serializer based on the requested format (json)
	ODataFormat format = ODataFormat.fromContentType(responseFormat);
	ODataSerializer serializer = odata.createSerializer(format);

	// 4th: Now serialize the content: transform from the EntitySet object
	// to InputStream
	EdmEntityType edmEntityType = edmEntitySet.getEntityType();
	ContextURL contextUrl = ContextURL.with().entitySet(edmEntitySet)
			.build();

	EntityCollectionSerializerOptions opts = EntityCollectionSerializerOptions
			.with().contextURL(contextUrl).build();
	InputStream serializedContent = serializer.entityCollection(
			edmEntityType, entitySet, opts);

	// Finally: configure the response object: set the body, headers and
	// status code
	response.setContent(serializedContent);
	response.setStatusCode(HttpStatusCode.OK.getStatusCode());
	response.setHeader(HttpHeader.CONTENT_TYPE,
			responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request, ODataResponse response, UriInfo uriInfo, ContentType responseFormat) throws ODataApplicationException, SerializerException {

		// 1st retrieve the requested EntitySet from the uriInfo (representation of the parsed URI)
		List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
		UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0); // in our example, the first segment is the EntitySet
		EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

		// 2nd: fetch the data from backend for this requested EntitySetName and deliver as EntitySet
		EntityCollection entityCollection = storage.readEntitySetData(edmEntitySet);

		// 3rd: create a serializer based on the requested format (json)
		ODataSerializer serializer = odata.createSerializer(responseFormat);

		// and serialize the content: transform from the EntitySet object to InputStream
		EdmEntityType edmEntityType = edmEntitySet.getEntityType();
		ContextURL contextUrl = ContextURL.with().entitySet(edmEntitySet).build();

		final String id = request.getRawBaseUri() + "/" + edmEntitySet.getName();
		EntityCollectionSerializerOptions opts =
				EntityCollectionSerializerOptions.with().id(id).contextURL(contextUrl).build();
		SerializerResult serializerResult = serializer.entityCollection(serviceMetadata, edmEntityType, entityCollection, opts);
		InputStream serializedContent = serializerResult.getContent();

		// 4th: configure the response object: set the body, headers and status code
		response.setContent(serializedContent);
		response.setStatusCode(HttpStatusCode.OK.getStatusCode());
		response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
	}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
private void readFunctionImportCollection(final ODataRequest request, final ODataResponse response, 
    final UriInfo uriInfo, final ContentType responseFormat) throws ODataApplicationException, SerializerException {
  
  // 1st step: Analyze the URI and fetch the entity collection returned by the function import
  // Function Imports are always the first segment of the resource path
  final UriResource firstSegment = uriInfo.getUriResourceParts().get(0);
  
  if(!(firstSegment instanceof UriResourceFunction)) {
    throw new ODataApplicationException("Not implemented", HttpStatusCode.NOT_IMPLEMENTED.getStatusCode(), 
        Locale.ENGLISH);
  }
  
  final UriResourceFunction uriResourceFunction = (UriResourceFunction) firstSegment;
  final EntityCollection entityCol = storage.readFunctionImportCollection(uriResourceFunction, serviceMetadata);
  
  // 2nd step: Serialize the response entity
  final EdmEntityType edmEntityType = (EdmEntityType) uriResourceFunction.getFunction().getReturnType().getType();
  final ContextURL contextURL = ContextURL.with().asCollection().type(edmEntityType).build();
  EntityCollectionSerializerOptions opts = EntityCollectionSerializerOptions.with().contextURL(contextURL).build();
  final ODataSerializer serializer = odata.createSerializer(responseFormat);
  final SerializerResult serializerResult = serializer.entityCollection(serviceMetadata, edmEntityType, entityCol, 
      opts); 

  // 3rd configure the response object
  response.setContent(serializerResult.getContent());
  response.setStatusCode(HttpStatusCode.OK.getStatusCode());
  response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request, ODataResponse response, UriInfo uriInfo, ContentType responseFormat) throws ODataApplicationException, SerializerException {

    // 1st we have retrieve the requested EntitySet from the uriInfo object (representation of the parsed service URI)
    List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
    UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0); // in our example, the first segment is the EntitySet
    EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

    // 2nd: fetch the data from backend for this requested EntitySetName // it has to be delivered as EntitySet object
    EntityCollection entitySet = getData(edmEntitySet);

    // 3rd: create a serializer based on the requested format (json)
    ODataSerializer serializer = odata.createSerializer(responseFormat);
    
    // 4th: Now serialize the content: transform from the EntitySet object to InputStream
    EdmEntityType edmEntityType = edmEntitySet.getEntityType();
    ContextURL contextUrl = ContextURL.with().entitySet(edmEntitySet).build();

    final String id = request.getRawBaseUri() + "/" + edmEntitySet.getName();
    EntityCollectionSerializerOptions opts =
        EntityCollectionSerializerOptions.with().id(id).contextURL(contextUrl).build();
    SerializerResult serializedContent = serializer.entityCollection(serviceMetadata, edmEntityType, entitySet, opts);

    // Finally: configure the response object: set the body, headers and status code
    response.setContent(serializedContent.getContent());
    response.setStatusCode(HttpStatusCode.OK.getStatusCode());
    response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
  }
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request, ODataResponse response, UriInfo uriInfo,
    ContentType responseFormat) throws ODataApplicationException, SerializerException {

  // 1st retrieve the requested EntitySet from the uriInfo (representation of the parsed URI)
  List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
  // in our example, the first segment is the EntitySet
  UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0);
  EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

  // 2nd: fetch the data from backend for this requested EntitySetName
  // it has to be delivered as EntitySet object
  EntityCollection entitySet = storage.readEntitySetData(edmEntitySet);

  // 3rd: create a serializer based on the requested format (json)
  ODataSerializer serializer = odata.createSerializer(responseFormat);

  // and serialize the content: transform from the EntitySet object to InputStream
  EdmEntityType edmEntityType = edmEntitySet.getEntityType();
  ContextURL contextUrl = ContextURL.with().entitySet(edmEntitySet).build();

  final String id = request.getRawBaseUri() + "/" + edmEntitySet.getName();
  EntityCollectionSerializerOptions opts =
      EntityCollectionSerializerOptions.with().id(id).contextURL(contextUrl).build();
  SerializerResult serializedContent = serializer.entityCollection(serviceMetadata, edmEntityType, entitySet, opts);

  // Finally: configure the response object: set the body, headers and status code
  response.setContent(serializedContent.getContent());
  response.setStatusCode(HttpStatusCode.OK.getStatusCode());
  response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
@Override
public void readEntityCollection(ODataRequest request, ODataResponse response, UriInfo uriInfo,
    ContentType responseFormat) throws ODataApplicationException, SerializerException {

  // 1st: retrieve the requested EntitySet from the uriInfo (representation of the parsed URI)
  List<UriResource> resourcePaths = uriInfo.getUriResourceParts();

  // in our example, the first segment is the EntitySet
  UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0);
  EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

  // 2nd: fetch the data from backend for this requested EntitySetName and deliver as EntitySet
  EntityCollection entityCollection = getData(edmEntitySet);
  EntityCollection modifiedEntityCollection = new EntityCollection();
  List<Entity> modifiedEntityList = new ArrayList<Entity>();

  modifiedEntityList.addAll(entityCollection.getEntities());

  // // 3rd: Apply system query option
  // // The system query options have to be applied in a defined order
  // // 3.1.) $filter
  // modifiedEntityList = applyFilterQueryOption(modifiedEntityList, uriInfo.getFilterOption());
  //
  // // 3.2.) $orderby
  // modifiedEntityList = applyOrderQueryOption(modifiedEntityList, uriInfo.getOrderByOption());
  //
  // // 3.3.) $count
  // modifiedEntityList = applyCountQueryOption(modifiedEntityCollection, modifiedEntityList,
  // uriInfo.getCountOption());
  //
  // // 3.4.) $skip
  // modifiedEntityList = applySkipQueryOption(modifiedEntityList, uriInfo.getSkipOption());
  //
  // // 3.5.) $top
  // modifiedEntityList = applyTopQueryOption(modifiedEntityList, uriInfo.getTopOption());
  //
  // // 3.6.) Server driven paging (not part of this tutorial)
  // // 3.7.) $expand
  // modifiedEntityList = applyExpandQueryOption(modifiedEntityList, edmEntitySet,
  // uriInfo.getExpandOption());
  // 3.8.) $select
  SelectOption selectOption = uriInfo.getSelectOption();

  // Set the (may) modified entityList to the new entity collection
  modifiedEntityCollection.getEntities().addAll(modifiedEntityList);

  // 4th: create a serializer based on the requested format (json)
  ODataSerializer serializer = odata.createSerializer(responseFormat);

  // we need the property names of the $select, in order to build the context URL
  EdmEntityType edmEntityType = edmEntitySet.getEntityType();
  String selectList = odata.createUriHelper().buildContextURLSelectList(edmEntityType,
      uriInfo.getExpandOption(), selectOption);
  ContextURL contextUrl =
      ContextURL.with().entitySet(edmEntitySet).selectList(selectList).build();

  // adding the selectOption to the serializerOpts will actually tell the lib to do the job
  final String id = request.getRawBaseUri() + "/" + edmEntitySet.getName();
  EntityCollectionSerializerOptions opts = EntityCollectionSerializerOptions.with()
      .contextURL(contextUrl).count(uriInfo.getCountOption()).select(selectOption)
      .expand(uriInfo.getExpandOption()).id(id).build();

  // and serialize the content: transform from the EntitySet object to InputStream
  SerializerResult serializerResult =
      serializer.entityCollection(serviceMetadata, edmEntityType, modifiedEntityCollection, opts);
  InputStream serializedContent = serializerResult.getContent();

  // 5th: configure the response object: set the body, headers and status code
  response.setContent(serializedContent);
  response.setStatusCode(HttpStatusCode.OK.getStatusCode());
  response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request, ODataResponse response, UriInfo uriInfo, 
    ContentType responseFormat) throws ODataApplicationException, SerializerException {

	// 1st: retrieve the requested EntitySet from the uriInfo (representation of the parsed URI)
	List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
	// in our example, the first segment is the EntitySet
	UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0); 
	EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

	// 2nd: fetch the data from backend for this requested EntitySetName and deliver as EntitySet
	EntityCollection entityCollection = storage.readEntitySetData(edmEntitySet);
	
	// 3rd: Check if filter system query option is provided and apply the expression if necessary
	FilterOption filterOption = uriInfo.getFilterOption();
	if(filterOption != null) {
		// Apply $filter system query option
		try {
		      List<Entity> entityList = entityCollection.getEntities();
		      Iterator<Entity> entityIterator = entityList.iterator();
		      
		      // Evaluate the expression for each entity
		      // If the expression is evaluated to "true", keep the entity otherwise remove it from the entityList
		      while (entityIterator.hasNext()) {
		    	  // To evaluate the the expression, create an instance of the Filter Expression Visitor and pass
		    	  // the current entity to the constructor
		    	  Entity currentEntity = entityIterator.next();
		    	  Expression filterExpression = filterOption.getExpression();
		    	  FilterExpressionVisitor expressionVisitor = new FilterExpressionVisitor(currentEntity);
		    	  
		    	  // Start evaluating the expression
		    	  Object visitorResult = filterExpression.accept(expressionVisitor);
		    	  
		    	  // The result of the filter expression must be of type Edm.Boolean
		    	  if(visitorResult instanceof Boolean) {
		    		  if(!Boolean.TRUE.equals(visitorResult)) {
		    		    // The expression evaluated to false (or null), so we have to remove the currentEntity from entityList
		    		    entityIterator.remove();
		    		  }
		    	  } else {
		    		  throw new ODataApplicationException("A filter expression must evaulate to type Edm.Boolean", 
		    		      HttpStatusCode.BAD_REQUEST.getStatusCode(), Locale.ENGLISH);
		    	  }
		      }

		    } catch (ExpressionVisitException e) {
		      throw new ODataApplicationException("Exception in filter evaluation",
		          HttpStatusCode.INTERNAL_SERVER_ERROR.getStatusCode(), Locale.ENGLISH);
		    }
	}
	
	// 4th: create a serializer based on the requested format (json)
	ODataSerializer serializer = odata.createSerializer(responseFormat);

	// and serialize the content: transform from the EntitySet object to InputStream
	EdmEntityType edmEntityType = edmEntitySet.getEntityType();
	ContextURL contextUrl = ContextURL.with().entitySet(edmEntitySet).build();

	final String id = request.getRawBaseUri() + "/" + edmEntitySet.getName();
	EntityCollectionSerializerOptions opts = EntityCollectionSerializerOptions.with()
			.contextURL(contextUrl).id(id).build();
	SerializerResult serializerResult = serializer.entityCollection(serviceMetadata, edmEntityType, entityCollection,
			opts);

	InputStream serializedContent = serializerResult.getContent();

	// 5th: configure the response object: set the body, headers and status code
	response.setContent(serializedContent);
	response.setStatusCode(HttpStatusCode.OK.getStatusCode());
	response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request, ODataResponse response,
    UriInfo uriInfo, ContentType responseFormat)
    throws ODataApplicationException, SerializerException {
  
  EdmEntitySet responseEdmEntitySet = null; // we'll need this to build the ContextURL
  EntityCollection responseEntityCollection = null; // we'll need this to set the response body

  // 1st retrieve the requested EntitySet from the uriInfo (representation of the parsed URI)
  List<UriResource> resourceParts = uriInfo.getUriResourceParts();
  int segmentCount = resourceParts.size();

  UriResource uriResource = resourceParts.get(0); // in our example, the first segment is the EntitySet
  if (!(uriResource instanceof UriResourceEntitySet)) {
    throw new ODataApplicationException("Only EntitySet is supported",
        HttpStatusCode.NOT_IMPLEMENTED.getStatusCode(), Locale.ROOT);
  }

  UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) uriResource;
  EdmEntitySet startEdmEntitySet = uriResourceEntitySet.getEntitySet();

  if (segmentCount == 1) { // this is the case for: DemoService/DemoService.svc/Categories
    responseEdmEntitySet = startEdmEntitySet; // the response body is built from the first (and only) entitySet

    // 2nd: fetch the data from backend for this requested EntitySetName and deliver as EntitySet
    responseEntityCollection = storage.readEntitySetData(startEdmEntitySet);
  } else if (segmentCount == 2) { // in case of navigation: DemoService.svc/Categories(3)/Products

    UriResource lastSegment = resourceParts.get(1); // in our example we don't support more complex URIs
    if (lastSegment instanceof UriResourceNavigation) {
      UriResourceNavigation uriResourceNavigation = (UriResourceNavigation) lastSegment;
      EdmNavigationProperty edmNavigationProperty = uriResourceNavigation.getProperty();
      // from Categories(1) to Products
      responseEdmEntitySet = Util.getNavigationTargetEntitySet(startEdmEntitySet, edmNavigationProperty);

      // 2nd: fetch the data from backend
      // first fetch the entity where the first segment of the URI points to
      List<UriParameter> keyPredicates = uriResourceEntitySet.getKeyPredicates();
      // e.g. for Categories(3)/Products we have to find the single entity: Category with ID 3
      Entity sourceEntity = storage.readEntityData(startEdmEntitySet, keyPredicates);
      // error handling for e.g. DemoService.svc/Categories(99)/Products
      if (sourceEntity == null) {
        throw new ODataApplicationException("Entity not found.",
            HttpStatusCode.NOT_FOUND.getStatusCode(), Locale.ROOT);
      }
      // then fetch the entity collection where the entity navigates to
      // note: we don't need to check uriResourceNavigation.isCollection(),
      // because we are the EntityCollectionProcessor
      responseEntityCollection = storage.getRelatedEntityCollection(sourceEntity, uriResourceNavigation);
    }
  } else { // this would be the case for e.g. Products(1)/Category/Products
    throw new ODataApplicationException("Not supported",
        HttpStatusCode.NOT_IMPLEMENTED.getStatusCode(), Locale.ROOT);
  }

  // 3rd: create and configure a serializer
  ContextURL contextUrl = ContextURL.with().entitySet(responseEdmEntitySet).build();
  final String id = request.getRawBaseUri() + "/" + responseEdmEntitySet.getName();
  EntityCollectionSerializerOptions opts = EntityCollectionSerializerOptions.with()
      .contextURL(contextUrl).id(id).build();
  EdmEntityType edmEntityType = responseEdmEntitySet.getEntityType();

  ODataSerializer serializer = odata.createSerializer(responseFormat);
  SerializerResult serializerResult = serializer.entityCollection(serviceMetadata, edmEntityType,
      responseEntityCollection, opts);

  // 4th: configure the response object: set the body, headers and status code
  response.setContent(serializerResult.getContent());
  response.setStatusCode(HttpStatusCode.OK.getStatusCode());
  response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request, ODataResponse response, UriInfo uriInfo, 
    ContentType responseFormat) throws ODataApplicationException, SerializerException {

	// 1st retrieve the requested EntitySet from the uriInfo (representation of the parsed URI)
	List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
	// in our example, the first segment is the EntitySet
	UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0); 
	EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

	// 2nd: fetch the data from backend for this requested EntitySetName and deliver as EntitySet
	EntityCollection entityCollection = storage.readEntitySetData(edmEntitySet);
	List<Entity> entityList = entityCollection.getEntities();
	
	// 3rd apply $orderby
	OrderByOption orderByOption = uriInfo.getOrderByOption();
	if (orderByOption != null) {
		List<OrderByItem> orderItemList = orderByOption.getOrders();
		final OrderByItem orderByItem = orderItemList.get(0); // in our example we support only one
		Expression expression = orderByItem.getExpression();
		if(expression instanceof Member){
			UriInfoResource resourcePath = ((Member)expression).getResourcePath();
			UriResource uriResource = resourcePath.getUriResourceParts().get(0);
			if (uriResource instanceof UriResourcePrimitiveProperty) {
				EdmProperty edmProperty = ((UriResourcePrimitiveProperty)uriResource).getProperty();
				final String sortPropertyName = edmProperty.getName();

				// do the sorting for the list of entities  
				Collections.sort(entityList, new Comparator<Entity>() {

					// we delegate the sorting to the native sorter of Integer and String
					public int compare(Entity entity1, Entity entity2) {
						int compareResult = 0;

						if(sortPropertyName.equals("ID")){
							Integer integer1 = (Integer) entity1.getProperty(sortPropertyName).getValue();
							Integer integer2 = (Integer) entity2.getProperty(sortPropertyName).getValue();
							
							compareResult = integer1.compareTo(integer2);
						}else{
							String propertyValue1 = (String) entity1.getProperty(sortPropertyName).getValue();
							String propertyValue2 = (String) entity2.getProperty(sortPropertyName).getValue();
							
							compareResult = propertyValue1.compareTo(propertyValue2);
						}

						// if 'desc' is specified in the URI, change the order of the list 
						if(orderByItem.isDescending()){
							return - compareResult; // just convert the result to negative value to change the order
						}
						
						return compareResult;
					}
				});
			}
		}
	}
	
	
	// 4th: create a serializer based on the requested format (json)
	ODataSerializer serializer = odata.createSerializer(responseFormat);

	// and serialize the content: transform from the EntitySet object to InputStream
	EdmEntityType edmEntityType = edmEntitySet.getEntityType();
	ContextURL contextUrl = ContextURL.with().entitySet(edmEntitySet).build();

	final String id = request.getRawBaseUri() + "/" + edmEntitySet.getName();
	EntityCollectionSerializerOptions opts =
			EntityCollectionSerializerOptions.with().id(id).contextURL(contextUrl).build();
   SerializerResult serializerResult = serializer.entityCollection(serviceMetadata, edmEntityType, 
                                                                   entityCollection, opts);
	InputStream serializedContent = serializerResult.getContent();

	// 5th: configure the response object: set the body, headers and status code
	response.setContent(serializedContent);
	response.setStatusCode(HttpStatusCode.OK.getStatusCode());
	response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request, ODataResponse response,
    UriInfo uriInfo, ContentType responseFormat)
    throws ODataApplicationException, SerializerException {
  
  EdmEntitySet responseEdmEntitySet = null; // we'll need this to build the ContextURL
  EntityCollection responseEntityCollection = null; // we'll need this to set the response body

  // 1st retrieve the requested EntitySet from the uriInfo (representation of the parsed URI)
  List<UriResource> resourceParts = uriInfo.getUriResourceParts();
  int segmentCount = resourceParts.size();

  UriResource uriResource = resourceParts.get(0); // in our example, the first segment is the EntitySet
  if (!(uriResource instanceof UriResourceEntitySet)) {
    throw new ODataApplicationException("Only EntitySet is supported",
        HttpStatusCode.NOT_IMPLEMENTED.getStatusCode(), Locale.ROOT);
  }

  UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) uriResource;
  EdmEntitySet startEdmEntitySet = uriResourceEntitySet.getEntitySet();

  if (segmentCount == 1) { // this is the case for: DemoService/DemoService.svc/Categories
    responseEdmEntitySet = startEdmEntitySet; // the response body is built from the first (and only) entitySet

    // 2nd: fetch the data from backend for this requested EntitySetName and deliver as EntitySet
    responseEntityCollection = storage.readEntitySetData(startEdmEntitySet);
  } else if (segmentCount == 2) { // in case of navigation: DemoService.svc/Categories(3)/Products

    UriResource lastSegment = resourceParts.get(1); // in our example we don't support more complex URIs
    if (lastSegment instanceof UriResourceNavigation) {
      UriResourceNavigation uriResourceNavigation = (UriResourceNavigation) lastSegment;
      EdmNavigationProperty edmNavigationProperty = uriResourceNavigation.getProperty();
      EdmEntityType targetEntityType = edmNavigationProperty.getType();
      // from Categories(1) to Products
      responseEdmEntitySet = Util.getNavigationTargetEntitySet(startEdmEntitySet, edmNavigationProperty);

      // 2nd: fetch the data from backend
      // first fetch the entity where the first segment of the URI points to
      List<UriParameter> keyPredicates = uriResourceEntitySet.getKeyPredicates();
      // e.g. for Categories(3)/Products we have to find the single entity: Category with ID 3
      Entity sourceEntity = storage.readEntityData(startEdmEntitySet, keyPredicates);
      // error handling for e.g. DemoService.svc/Categories(99)/Products
      if (sourceEntity == null) {
        throw new ODataApplicationException("Entity not found.",
            HttpStatusCode.NOT_FOUND.getStatusCode(), Locale.ROOT);
      }
      // then fetch the entity collection where the entity navigates to
      // note: we don't need to check uriResourceNavigation.isCollection(),
      // because we are the EntityCollectionProcessor
      responseEntityCollection = storage.getRelatedEntityCollection(sourceEntity, targetEntityType);
    }
  } else { // this would be the case for e.g. Products(1)/Category/Products
    throw new ODataApplicationException("Not supported",
        HttpStatusCode.NOT_IMPLEMENTED.getStatusCode(), Locale.ROOT);
  }

  // 3rd: create and configure a serializer
  ContextURL contextUrl = ContextURL.with().entitySet(responseEdmEntitySet).build();
  final String id = request.getRawBaseUri() + "/" + responseEdmEntitySet.getName();
  EntityCollectionSerializerOptions opts = EntityCollectionSerializerOptions.with()
      .contextURL(contextUrl).id(id).build();
  EdmEntityType edmEntityType = responseEdmEntitySet.getEntityType();

  ODataSerializer serializer = odata.createSerializer(responseFormat);
  SerializerResult serializerResult = serializer.entityCollection(serviceMetadata, edmEntityType,
      responseEntityCollection, opts);

  // 4th: configure the response object: set the body, headers and status code
  response.setContent(serializerResult.getContent());
  response.setStatusCode(HttpStatusCode.OK.getStatusCode());
  response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}
 

import org.apache.olingo.server.api.serializer.ODataSerializer; //导入方法依赖的package包/类
public void readEntityCollection(ODataRequest request, ODataResponse response, UriInfo uriInfo,
    ContentType responseFormat) throws ODataApplicationException, SerializerException {

  // 1st retrieve the requested EntitySet from the uriInfo (representation of the parsed URI)
  List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
  // in our example, the first segment is the EntitySet
  UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0);
  EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

  // 2nd: fetch the data from backend for this requested EntitySetName and deliver as EntitySet
  EntityCollection entityCollection = storage.readEntitySetData(edmEntitySet);

  // 3rd: apply System Query Options
  // modify the result set according to the query options, specified by the end user
  List<Entity> entityList = entityCollection.getEntities();
  EntityCollection returnEntityCollection = new EntityCollection();

  // handle $count: always return the original number of entities, without considering $top and $skip
  CountOption countOption = uriInfo.getCountOption();
  if (countOption != null) {
    boolean isCount = countOption.getValue();
    if (isCount) {
      returnEntityCollection.setCount(entityList.size());
    }
  }
  
  // handle $skip
  SkipOption skipOption = uriInfo.getSkipOption();
  if (skipOption != null) {
    int skipNumber = skipOption.getValue();
    if (skipNumber >= 0) {
      if(skipNumber <= entityList.size()) {
        entityList = entityList.subList(skipNumber, entityList.size());
      } else {
        // The client skipped all entities
        entityList.clear();
      }
    } else {
      throw new ODataApplicationException("Invalid value for $skip", HttpStatusCode.BAD_REQUEST.getStatusCode(),
          Locale.ROOT);
    }
  }
  
  // handle $top
  TopOption topOption = uriInfo.getTopOption();
  if (topOption != null) {
    int topNumber = topOption.getValue();
    if (topNumber >= 0) {
      if(topNumber <= entityList.size()) {
        entityList = entityList.subList(0, topNumber);
      }  // else the client has requested more entities than available => return what we have
    } else {
      throw new ODataApplicationException("Invalid value for $top", HttpStatusCode.BAD_REQUEST.getStatusCode(),
          Locale.ROOT);
    }
  }

  // after applying the system query options, create the EntityCollection based on the reduced list
  for (Entity entity : entityList) {
    returnEntityCollection.getEntities().add(entity);
  }

  // 4th: create a serializer based on the requested format (json)
  ODataSerializer serializer = odata.createSerializer(responseFormat);

  // and serialize the content: transform from the EntitySet object to InputStream
  EdmEntityType edmEntityType = edmEntitySet.getEntityType();
  ContextURL contextUrl = ContextURL.with().entitySet(edmEntitySet).build();

  final String id = request.getRawBaseUri() + "/" + edmEntitySet.getName();
  EntityCollectionSerializerOptions opts =
      EntityCollectionSerializerOptions.with().contextURL(contextUrl).id(id).count(countOption).build();
  SerializerResult serializerResult =
      serializer.entityCollection(serviceMetadata, edmEntityType, returnEntityCollection, opts);
  InputStream serializedContent = serializerResult.getContent();

  // 5th: configure the response object: set the body, headers and status code
  response.setContent(serializedContent);
  response.setStatusCode(HttpStatusCode.OK.getStatusCode());
  response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
}