实体属性参考

Entity employee = new Entity("Employee");
ArrayList<String> favoriteFruit = new ArrayList<String>();
favoriteFruit.add("Pear");
favoriteFruit.add("Apple");
employee.setProperty("favoriteFruit", favoriteFruit);
datastore.put(employee);

// Sometime later
employee = datastore.get(employee.getKey());
@SuppressWarnings("unchecked") // Cast can't verify generic type.
    ArrayList<String> retrievedFruits = (ArrayList<String>) employee
    .getProperty("favoriteFruit");

// Entity employee = ...;
EmbeddedEntity embeddedContactInfo = new EmbeddedEntity();

embeddedContactInfo.setProperty("homeAddress", "123 Fake St, Made, UP 45678");
embeddedContactInfo.setProperty("phoneNumber", "555-555-5555");
embeddedContactInfo.setProperty("emailAddress", "test@example.com");

employee.setProperty("contactInfo", embeddedContactInfo);

// Entity employee = ...;
// Entity contactInfo = ...;
EmbeddedEntity embeddedContactInfo = new EmbeddedEntity();

embeddedContactInfo.setKey(contactInfo.getKey()); // Optional, used so we can recover original.
embeddedContactInfo.setPropertiesFrom(contactInfo);

employee.setProperty("contactInfo", embeddedContactInfo);

Entity employee = datastore.get(employeeKey);
EmbeddedEntity embeddedContactInfo = (EmbeddedEntity) employee.getProperty("contactInfo");

Key infoKey = embeddedContactInfo.getKey();
Entity contactInfo = new Entity(infoKey);
contactInfo.setPropertiesFrom(embeddedContactInfo);