介绍
有两种方法更新啦。第一种： insert/save 。第二种： update operation。
下面开始讨论。.
Updating (on the server)
当你调用update方法时，你其实就是发生一个修改命令给数据库。作用？当然是修改已存在的数据啦。
interface Datastore {
...
/** updates all entities found with the operations*/
<T> UpdateResults<T> update(Query<T> query, UpdateOperations<T> ops);
/** updates all entities found with the operations; if nothing is found insert the update as an entity if "createIfMissing" is true*/
<T> UpdateResults<T> update(Query<T> query, UpdateOperations<T> ops, boolean createIfMissing);
/** updates the first entity found with the operations*/
<T> UpdateResults<T> updateFirst(Query<T> query, UpdateOperations<T> ops);
/** updates the first entity found with the operations; if nothing is found insert the update as an entity if "createIfMissing" is true*/
<T> UpdateResults<T> updateFirst(Query<T> query, UpdateOperations<T> ops, boolean createIfMissing);
/** updates the first entity found with the operations; if nothing is found insert the update as an entity if "createIfMissing" is true*/
<T> UpdateResults<T> updateFirst(Query<T> query, T entity, boolean createIfMissing);
}
public interface UpdateOperations<T> {
/** sets the field value */
UpdateOperations<T> set(String fieldExpr, Object value);
/** removes the field */
UpdateOperations<T> unset(String fieldExpr);
/** adds the value to an array field*/
UpdateOperations<T> add(String fieldExpr, Object value);
UpdateOperations<T> add(String fieldExpr, Object value, boolean addDups);
/** adds the values to an array field*/
UpdateOperations<T> addAll(String fieldExpr, List<?> values, boolean addDups);
/** removes the first value from the array*/
UpdateOperations<T> removeFirst(String fieldExpr);
/** removes the last value from the array*/
UpdateOperations<T> removeLast(String fieldExpr);
/** removes the value from the array field*/
UpdateOperations<T> removeAll(String fieldExpr, Object value);
/** removes the values from the array field*/
UpdateOperations<T> removeAll(String fieldExpr, List<?> values);
/** decrements the numeric field by 1*/
UpdateOperations<T> dec(String fieldExpr);
/** increments the numeric field by 1*/
UpdateOperations<T> inc(String fieldExpr);
/** increments the numeric field by value (negatives are allowed)*/
UpdateOperations<T> inc(String fieldExpr, Number value);
}
The Field Expression
属性表达式可以作用于所有的操作。可以是一个的属性，也可以是点嵌套的属性。你也可以使用 ($)在属性表达式中。Samples initialization
Morphia morphia = new Morphia();
morphia.map(Hotel.class).map(Address.class);
Datastore datastore = morphia.createDatastore("MorphiaSampleDb");
Hotel hotel = new Hotel("Fairmont", 3, new Address("1 Rideau Street", "Ottawa", "K1N8S7", "Canada"));
datastore.save(hotel);
UpdateOperations<Hotel> ops;
// This query will be used in the samples to restrict the update operations to only the hotel we just created.
// If this was not supplied, by default the update() operates on all documents in the collection.
// We could use any field here but _id will be unique and mongodb by default puts an index on the _id field so this should be fast!
Query<Hotel> updateQuery = datastore.createQuery(Hotel.class).field("_id").equal(hotel.getId());
// The Mapper class also provides a public static of the default _id field name for us...
Query<Hotel> updateQuery = datastore.createQuery(Hotel.class).field(Mapper.ID_KEY).equal(hotel.getId());
注意：使用的是 equal()，而不是 equals()
@Entity("hotels")
public class Hotel
{
@Id
private ObjectId id;
private String name;
private int stars;
@Embedded
private Address address;
@Embedded
List<Integer> roomNumbers = new ArrayList<Integer>();
// ... getters and setters
}
@Embedded
public class Address
{
private String street;
private String city;
private String postalCode;
private String country;
// ... getters and setters
}
set/unset
// change the name of the hotel
ops = datastore.createUpdateOperations(Hotel.class).set("name", "Fairmont Chateau Laurier");
datastore.update(updateQuery, ops);
// also works for embedded documents, change the name of the city in the address
ops = datastore.createUpdateOperations(Hotel.class).set("address.city", "Ottawa");
datastore.update(updateQuery, ops);
// remove the name property from the document
// causes the next load of the Hotel to have name = null
ops = datastore.createUpdateOperations(Hotel.class).unset("name");
datastore.update(updateQuery, ops);
inc/dec
// increment 'stars' by 1
ops = datastore.createUpdateOperations(Hotel.class).inc("stars");
datastore.update(updateQuery, ops);
// increment 'stars' by 4
ops = datastore.createUpdateOperations(Hotel.class).inc("stars", 4);
datastore.update(updateQuery, ops);
// decrement 'stars' by 1
ops = datastore.createUpdateOperations(Hotel.class).dec("stars"); // same as .inc("stars", -1)
datastore.update(updateQuery, ops);
// decrement 'stars' by 4
ops = datastore.createUpdateOperations(Hotel.class).inc("stars", -4);
datastore.update(updateQuery, ops);
add/All
// push a value onto an array() (+v 0.95)
// same as .add("roomNumbers", 11, false)
ops = datastore.createUpdateOperations(Hotel.class).add("roomNumbers", 11);
datastore.update(updateQuery, ops); // [ 11 ]
当你向一个不是数组的属性，进行数组的操作。会报错的。
ops = datastore.createUpdateOperations(Hotel.class).set("roomNumbers", 11);
datastore.update(updateQuery, ops);
// causes error since 'roomNumbers' is not an array at this point
ops = datastore.createUpdateOperations(Hotel.class).add("roomNumbers", 11, false);
datastore.update(updateQuery, ops); // causes error
// delete the property
ops = datastore.createUpdateOperations(Hotel.class).unset("roomNumbers");
datastore.update(updateQuery, ops);
// use the 3rd parameter to add duplicates
// add to end of array, same as add()
ops = datastore.createUpdateOperations(Hotel.class).add("roomNumbers", 11, false);
datastore.update(updateQuery, ops); // [ 11 ]
// no change since its a duplicate... doesn't cause error
ops = datastore.createUpdateOperations(Hotel.class).add("roomNumbers", 11, false);
datastore.update(updateQuery, ops); // [ 11 ]
// push onto the end of the array
ops = datastore.createUpdateOperations(Hotel.class).add("roomNumbers", 12, false);
datastore.update(updateQuery, ops); // [ 11, 12 ]
// add even if its a duplicate
ops = datastore.createUpdateOperations(Hotel.class).add("roomNumbers", 11, true);
datastore.update(updateQuery, ops); // [ 11, 12, 11 ]
removeFirst/Last/All
//given roomNumbers = [ 1, 2, 3 ]
ops = datastore.createUpdateOperations(Hotel.class).removeFirst("roomNumbers");
datastore.update(updateQuery, ops); // [ 2, 3 ]
//given roomNumbers = [ 1, 2, 3 ]
ops = datastore.createUpdateOperations(Hotel.class).removeLast("roomNumbers");
datastore.update(updateQuery, ops); // [ 1, 2 ]
ops = datastore.createUpdateOperations(Hotel.class).removeLast("roomNumbers");
datastore.update(updateQuery, ops); // [ 1 ]
ops = datastore.createUpdateOperations(Hotel.class).removeLast("roomNumbers");
datastore.update(updateQuery, ops); // [] empty array
//given roomNumbers = [ 1, 2, 3, 3 ]
ops = datastore.createUpdateOperations(Hotel.class).removeAll("roomNumbers", 3);
datastore.update(updateQuery, ops); // [ 1, 2 ]
//given roomNumbers = [ 1, 2, 3, 3 ]
ops = datastore.createUpdateOperations(Hotel.class).removeAll("roomNumbers", Arrays.asList(2, 3));
datastore.update(updateQuery, ops); // [ 1 ]
Multiple Operations
你也可以在一个operation里面做多个操作。
//set city to Ottawa and increment stars by 1
ops = datastore.createUpdateOperations(Hotel.class).set("city", "Ottawa").inc("stars");
datastore.update(updateQuery, ops);
//if you perform multiple operations in one command on the same property, results will vary
ops = datastore.createUpdateOperations(Hotel.class).inc("stars", 50).inc("stars"); //increments by 1
ops = datastore.createUpdateOperations(Hotel.class).inc("stars").inc("stars", 50); //increments by 50
//you can't apply conflicting operations to the same property
ops = datastore.createUpdateOperations(Hotel.class).set("stars", 1).inc("stars", 50); //causes error
updateFirst method
In the default driver and shell this is the default behavior. In Morphia we feel like updating all the results of the query is a better default (see below).
{ name: "Fairmont", stars: 5}, { name: "Last Chance", stars: 3 }
ops = datastore.createUpdateOperations(Hotel.class).inc("stars", 50);
// (+v 0.95 now takes into account the order())
// morphia exposes a specific updateFirst to update only the first hotel matching the query
datastore.updateFirst(datastore.find(Hotel.class).order("stars"), ops); // update only Last Chance
datastore.updateFirst(datastore.find(Hotel.class).order("-stars"), ops); // update only Fairmont
//default shell version is to match first
//shell version has a multi to indicate to update all matches, not just first
//to mimic morphia operation, set multi = false
db.collection.update( criteria, objNew, upsert, multi );
update method
ops = datastore.createUpdateOperations(Hotel.class).inc("stars", 50);
// morphia default update is to update all the hotels
datastore.update(datastore.createQuery(Hotel.class), ops); //increments all hotels
//equivalent morphia shell version is... upsert = false, multi = true
db.collection.update( criteria, objNew, false, true );
createIfMissing (overload parameter)
all of the update methods are overloaded and accept a "createIfMissing" parameter
ops = datastore.createUpdateOperations(Hotel.class).inc("stars", 50);
//update, if not found create it
datastore.updateFirst(datastore.createQuery(Hotel.class).field("stars").greaterThan(100), ops, true);
// creates { "_id" : ObjectId("4c60629d2f1200000000161d"), "stars" : 50 }
//equivalent morphia shell version is... upsert = true
db.collection.update( criteria, objNew, true, multi );