java development with mongodb
DESCRIPTION
TRANSCRIPT
Java Development
Go.. Go… JVM!
Library Choices Raw MongoDB Driver
Map<String, Object> view of objects Rough but dynamic
Morphia (type-safe mapper) POJOs Annotation based (similar to JPA) Syntactic sugar and helpers
Others Code generators, other jvm languages
MongoDB Java Driver BSON Package
Types Encode/Decode DBObject (Map<String, Object>)
Nested Maps Directly encoded to binary format (BSON)
MongoDB Package Mongo DBObject (BasicDBObject/Builder) DB/DBColletion DBQuery/DBCursor
BSON Package Types
int and long Array/ArrayList String byte[] – binData Double (IEEE 754 FP) Date (secs since epoch) Null Boolean JavaScript String Regex
MongoDB Package Mongo
Connection, ThreadSafe WriteConcern*
DB Auth, Collections getLastError() Command(), eval() RequestStart/Done
DBCollection Insert/Save/Find/Remove/Update/FindAndModify ensureIndex
Simple ExampleDBCollection coll = new Mongo().getDB(“test”);coll.save(
new BasicDBObjectBuilder(“name”, “scott”).append(“sex”, “male”).append(“height”, 178)).get());
Simple Example, AgainDBCollection coll = new Mongo().getDB(“test”);
Map<String, Object> fields = new …fields.add(“name”, “scott”); fields.add(“sex”, “male”);fields.add(“height”, 178);
coll.insert(new BasicDBObject(fields));
DBObject <-> (B/J)SON{name:”scott”, sex:“male”, height: 178 }
new BasicDBObjectBuilder().append(“name”, “scott”) .append(“sex”, “male”) .append(“height”, 178) .get();
String name = (String)dbObj.get(“name”);
JSON.parse(…)DBObject dbObj = JSON.parse(“
{‘name’:’scott’, ‘height’: 178, ‘sex’:’male’}”);
ListsDBObject dbObj = JSON.parse(“
{‘name’:’scott’, height: 178, sex:’male’}”);
List<String> activities = new …activities.add(“mongodb”);activities.add(“java”);dbObj.put(“activities”, activities);
{…, activities: [‘mongodb’, ‘java’]}
Maps of Maps Can represent object graph/tree Always keyed off String (field)
Morphia: MongoDB Mapper Maps POJO Type-safe Access Patterns: DAO/Datastore/??? Data Types Performs well JPA like Many concepts came from Objectify (GAE)
Annotations @Entity(“collectionName”) @Id @Transient (not transient) @Indexed(…) @Property(“fieldAlias”) @AlsoLoad({aliases}) @Reference @Serialized [@Embedded]
Lifecycle Events @PrePersist @PreSave @PostPersist @PreLoad @PostLoad
EntityListeners EntityInterceptor
Basic POJO@Entityclass Person { @Id String name; SexEnum sex; @Indexed Integer height;}
Datastore Basics get(class, id) find(class, […]) save(entity, […]) delete(query) getCount(query) update/First(query, upOps) findAndModify/Delete(query, upOps)
Add, Get, DeletePerson me = new Person(“scott”, Sex.Male,
179)
Datastore ds = new Morphia().createDatastore()
ds.save(me);
Person meAgain = ds.get(Person.class, “scott”)
ds.delete(me);
QueriesDatastore ds = …
Query q = ds.createQuery(Person.class);
q.field(“height”).greaterThan(155).limit(5);
for(Person p : q.fetch()) print(p);
Person me = q.field(“name”).startsWith(“sc”).get();
UpdateDatastore ds = …Query q = ds.find(Person.class, “name”,
“scott”);UpdateOperation uo =
ds.createUpdateOperations(cls)
uo.set(“city”, “seattle”).set(“lastUpdated”, new Date());
UpdateResults res = ds.update(q, uo);if(res.getUpdatedCount() > 0) //do something?
Update Operations set(field, val) unset(field)
inc(field, [val]) dec(field)
add(field, val) addAdd(field, vals)
removeFirst/Last(field) removeAll(field, vals)
Relationships [@Embedded]
Loaded/Saved with Entity Update
@Reference Stored as DBRef(s) Loaded with Entity Not automatically saved
Key<T> (DBRef) Stored as DBRef(s) Just a link, but resolvable by Datastore/Query
