MongoDB基于Morphia （ 一）常用操作
转载自：：https://blog.csdn.net/small_love/article/details/6628200
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Introduction
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Updating (on the server)
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The Field Expression
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Samples initialization
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set/unset
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inc/dec
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add/All
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removeFirst/Last/All
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Multiple Operations
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updateFirst method
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update method
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createIfMissing (overload parameter)
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简介
这个有两个修改你的数据库的方法。你可以insert/save一个完整的实体，或者通过update操作。我们将在一下讨论。
Updating（On the server）
总之，当你通过Datesote调用update方法时就会向MongoDB服务器发送一个修改已存在数据的指令。
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interface Datastore {
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…
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/** updates all entities found with the operations*/
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UpdateResults update(Query query, UpdateOperations ops) ;
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/** updates all entities found with the operations; if nothing is found insert the update as an entity if “createIfMissing” is true*/
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UpdateResults update(Query query, UpdateOperations ops, boolean createIfMissing) ;
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/** updates the first entity found with the operations*/
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UpdateResults updateFirst(Query query, UpdateOperations ops) ;
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/** updates the first entity found with the operations; if nothing is found insert the update as an entity if “createIfMissing” is true*/
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UpdateResults updateFirst(Query query, UpdateOperations ops, boolean createIfMissing) ;
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/** updates the first entity found with the operations; if nothing is found insert the update as an entity if “createIfMissing” is true*/
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UpdateResults updateFirst(Query query, T entity, boolean createIfMissing) ;
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}
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public
interface UpdateOperations<T> {
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/** sets the field value */
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UpdateOperations
set(String fieldExpr, Object value) ;
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/** removes the field */
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UpdateOperations
unset(String fieldExpr) ;
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/** adds the value to an array field*/
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UpdateOperations
add(String fieldExpr, Object value) ;
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UpdateOperations
add(String fieldExpr, Object value, boolean addDups) ;
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/** adds the values to an array field*/
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UpdateOperations
addAll(String fieldExpr, List values, boolean addDups) ;
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/** removes the first value from the array*/
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UpdateOperations
removeFirst(String fieldExpr) ;
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/** removes the last value from the array*/
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UpdateOperations
removeLast(String fieldExpr) ;
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/** removes the value from the array field*/
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UpdateOperations
removeAll(String fieldExpr, Object value) ;
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/** removes the values from the array field*/
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UpdateOperations
removeAll(String fieldExpr, List values) ;
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/** decrements the numeric field by 1*/
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UpdateOperations
dec(String fieldExpr) ;
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/** increments the numeric field by 1*/
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UpdateOperations
inc(String fieldExpr) ;
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/** increments the numeric field by value (negatives are allowed)*/
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UpdateOperations
inc(String fieldExpr, Number value) ;
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}
The Field Expression
属性表达式是用在所有的操作上的，可以是单个的属性名，也可以是用点“.”连接的嵌套属性。在表达式中你也可以使用位置操作副($)。在属性
表达式中没有标准，你可以使用任何在MongoDB服务端有效符号。
事例初始化
一下所有的实例创建的连接和Morphia实例都使用的一下代码。
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Morphia morphia =
new Morphia();
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morphia.map(Hotel.class).map(Address.class);
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Datastore datastore = morphia.createDatastore(
“MorphiaSampleDb”);
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Hotel hotel =
new Hotel(
“Fairmont”,
3,
new Address(
“1 Rideau Street”,
“Ottawa”,
“K1N8S7”,
“Canada”));
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datastore.save(hotel);
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UpdateOperations
ops;
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// This query will be used in the samples to restrict the update operations to only the hotel we just created.
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// If this was not supplied, by default the update() operates on all documents in the collection.
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// 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!
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Query
updateQuery = datastore.createQuery(Hotel.class).field(
“_id”).equal(hotel.getId());
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// The Mapper class also provides a public static of the default _id field name for us…
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Query
updateQuery = datastore.createQuery(Hotel.class).field(Mapper.ID_KEY).equal(hotel.getId());
注意： 使用的是 equal() 而不是 equals()。
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@Entity(
“hotels”)
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public
class Hotel
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{
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@Id
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private ObjectId id;
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private String name;
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private
int stars;
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@Embedded
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private Address address;
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@Embedded
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List
roomNumbers =
new ArrayList();
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// … getters and setters
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}
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@Embedded
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public
class Address
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{
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private String street;
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private String city;
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private String postalCode;
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private String country;
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// … getters and setters
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}
set/unset
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// 改变Hotel的name属性值
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ops = datastore.createUpdateOperations(Hotel.class).set(
“name”,
“Fairmont Chateau Laurier”);
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datastore.update(updateQuery, ops);
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//也可以操作嵌套文档， 改变address的city属性值
ops = datastore.createUpdateOperations(Hotel.class).set("address.city", "Ottawa");
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datastore.update(updateQuery, ops);
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// 删除Hotel的name属性值
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// 当下会访问Hotel时name属性为null
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ops = datastore.createUpdateOperations(Hotel.class).unset(
"name");
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datastore.update(updateQuery, ops);
inc/dec
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// ‘stars’属性增长一
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ops = datastore.createUpdateOperations(Hotel.class).inc(
“stars”);
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datastore.update(updateQuery, ops);
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// ‘stars’属性值增长4
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ops = datastore.createUpdateOperations(Hotel.class).inc(
“stars”,
4);
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datastore.update(updateQuery, ops);
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// ‘stars’属性值减少1
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ops = datastore.createUpdateOperations(Hotel.class).dec(
“stars”);
// 和 .inc(“stars”, -1) 相同
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datastore.update(updateQuery, ops);
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// ‘stars’属性值减少4
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ops = datastore.createUpdateOperations(Hotel.class).inc(
“stars”, -
4);
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datastore.update(updateQuery, ops);
add/All
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// 把一个值放入到数组中 array() (+v 0.95)
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// same as .add(“roomNumbers”, 11, false)
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ops = datastore.createUpdateOperations(Hotel.class).add(
“roomNumbers”,
11);
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datastore.update(updateQuery, ops);
// [ 11 ]
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ops = datastore.createUpdateOperations(Hotel.class).set(
“roomNumbers”,
11);
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datastore.update(updateQuery, ops);
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// 由于没有rooNumbers数组将会引起错误
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ops = datastore.createUpdateOperations(Hotel.class).add(
“roomNumbers”,
11,
false);
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datastore.update(updateQuery, ops);
// causes error
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// 删除roomNummbers属性
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ops = datastore.createUpdateOperations(Hotel.class).unset(
“roomNumbers”);
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datastore.update(updateQuery, ops);
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// use the 3rd parameter to add duplicates
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// add to end of array, same as add()
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ops = datastore.createUpdateOperations(Hotel.class).add(
“roomNumbers”,
11,
false);
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datastore.update(updateQuery, ops);
// [ 11 ]
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// no change since its a duplicate… doesn’t cause error
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ops = datastore.createUpdateOperations(Hotel.class).add(
“roomNumbers”,
11,
false);
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datastore.update(updateQuery, ops);
// [ 11 ]
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// push onto the end of the array
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ops = datastore.createUpdateOperations(Hotel.class).add(
“roomNumbers”,
12,
false);
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datastore.update(updateQuery, ops);
// [ 11, 12 ]
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// add even if its a duplicate
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ops = datastore.createUpdateOperations(Hotel.class).add(
“roomNumbers”,
11,
true);
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datastore.update(updateQuery, ops);
// [ 11, 12, 11 ]
removeFirst/Last/All
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//given roomNumbers = [ 1, 2, 3 ]
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ops = datastore.createUpdateOperations(Hotel.class).removeFirst(
“roomNumbers”);
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datastore.update(updateQuery, ops);
// [ 2, 3 ]
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//given roomNumbers = [ 1, 2, 3 ]
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ops = datastore.createUpdateOperations(Hotel.class).removeLast(
“roomNumbers”);
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datastore.update(updateQuery, ops);
// [ 1, 2 ]
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ops = datastore.createUpdateOperations(Hotel.class).removeLast(
“roomNumbers”);
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datastore.update(updateQuery, ops);
// [ 1 ]
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ops = datastore.createUpdateOperations(Hotel.class).removeLast(
“roomNumbers”);
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datastore.update(updateQuery, ops);
// [] empty array
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//given roomNumbers = [ 1, 2, 3, 3 ]
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ops = datastore.createUpdateOperations(Hotel.class).removeAll(
“roomNumbers”,
3);
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datastore.update(updateQuery, ops);
// [ 1, 2 ]
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//given roomNumbers = [ 1, 2, 3, 3 ]
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ops = datastore.createUpdateOperations(Hotel.class).removeAll(
“roomNumbers”, Arrays.asList(
2,
3));
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datastore.update(updateQuery, ops);
// [ 1 ]
Multiple Operations
你也可以在一个update指令中执行多个updae操作。
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//设置城市名称为Ottawa和是stars的增长1
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ops = datastore.createUpdateOperations(Hotel.class).set(
“city”,
“Ottawa”).inc(
“stars”);
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datastore.update(updateQuery, ops);
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//如果你在同一个属性上执行多次同样的指令操作，结果将会变化，即:只有最后一次有效
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ops = datastore.createUpdateOperations(Hotel.class).inc(
“stars”,
50).inc(
“stars”);
//stars只增长1
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ops = datastore.createUpdateOperations(Hotel.class).inc(
“stars”).inc(
“stars”,
50);
//stars只增长50
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//你不能在同一个属性上执行相矛盾的操作。
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ops = datastore.createUpdateOperations(Hotel.class).set(
“stars”,
1).inc(
“stars”,
50);
//引起错误
{name: “Fairmont”, stars: 5}, {name: “Last Chance”, stars: 3}
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ops = datastore.createUpdateOperations(Hotel.class).inc(
“stars”,
50);
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// (+v 0.95 now takes into account the order())
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// morphia 执行updateFirst方法仅仅执行第一个符合查询条件的数据项
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datastore.updateFirst(datastore.find(Hotel.class).order(
“stars”), ops);
//仅仅修改Last Chance
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datastore.updateFirst(datastore.find(Hotel.class).order(
“-stars”), ops);
// 仅仅修改 Fairmont
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//default shell version is to match first
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//shell version has a multi to indicate to update all matches, not just first
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//to mimic morphia operation, set multi = false
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db.collection.update( criteria, objNew, upsert, multi );
update 方法
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ops = datastore.createUpdateOperations(Hotel.class).inc(
“stars”,
50);
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// morphia 默认的update是修改所有的Hotels
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datastore.update(datastore.createQuery(Hotel.class), ops);
//所有的hotel都会增长
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//equivalent morphia shell version is... upsert = false, multi = true
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db.collection.update( criteria, objNew,
false,
true );
所有的update都被重载支持一个”createIfMissing”参数。
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ops = datastore.createUpdateOperations(Hotel.class).inc(
“stars”,
50);
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//修改， 如果没有找到就添加一个。
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datastore.updateFirst(datastore.createQuery(Hotel.class).field(
“stars”).greaterThan(
100), ops,
true);
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// creates { “_id” : ObjectId(“4c60629d2f1200000000161d”), “stars” : 50 }
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//equivalent morphia shell version is… upsert = true
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db.collection.update( criteria, objNew,
true, multi );
原文连接：http://code.google.com/p/morphia/wiki/Updating