DevNation'15 - Using Lambda Expressions to Query a Datastore

Using Lambda Expressions to Query a Datastore Xavier Coulon - Red Hat @xcoulon

The idea Lambda Expressions: • provide type safety • describe the "what", not the "how"

The idea u -> ( u.firstName.equals("john") && u.lastName.equals("doe")) || u.userName.equals("jdoe")) final List<User> users = userCollection.filter( u -> ( u.firstName.equals("john") && u.lastName.equals("doe")) || u.userName.equals("jdoe")).toList();

Introducing project Lambdamatic

Building blocks • Metamodel generation • Lambda Expression analysis

Metamodel generation (à la JPA)

package com.example.domain; public class User { private String id; private String firstName; private String lastName; private String userName; } Metamodel generation package com.example.domain; @Document(collection="users") public class User { @DocumentId private String id; @DocumentField private String firstName; private String lastName; @DocumentField(name="uName") private String userName; } package com.example.domain; @Generated(value="LambdamaticAnnotationsProcessor") public class QUser implements QueryMetadata<User> { @DocumentField(name="_id") public StringField firstName; @DocumentField(name="firstName") public StringField firstName; @DocumentField(name="lastName") public StringField lastName; @DocumentField(name="uName") public StringField userName; } Query Metadata class generation

Metamodel generation package com.example.domain; @Generated(value="o.l.m.a.DocumentAnnotationProcessor") public class UserCollection extends LambdamaticMongoCollectionImpl<User, QUser> { public UserCollection(final MongoClient mongoClient, final String databaseName) { super(mongoClient, databaseName, "users", User.class); } } Collection class package com.example.domain; @Document(collection="users") public class User { @DocumentId private String id; @DocumentField private String firstName; private String lastName; @DocumentField(name="uName") private String userName; }

Metamodel generation CDI Integration @Generated(value="org.lambdamatic.mongodb.apt.DocumentAnnotationProcessor") @ApplicationScoped public class UserCollectionProducer { @Produces public UserCollection getUserCollection(final MongoClient mongoClient, final MongoClientConfiguration mongoClientConfiguration) { return new UserCollection(mongoClient, mongoClientConfiguration.getDatabaseName(), "users"); } }

final List<User> users = userCollection.filter( u -> ( u.firstName.equals("john") && u.lastName.equals("doe")) || u.userName.equals("jdoe")).toList(); Metamodel in action public class UserCollection extends LambdamaticMongoCollectionImpl<User, QUser> { ... } package com.example.domain; @Generated(value="LambdamaticAnnotationsProcessor") public class QUser implements QueryMetadata<User> { @DocumentField(name="_id") public StringField firstName; @DocumentField(name="firstName") public StringField firstName; ... }

Metamodel benefits Geospatial queries

Metamodel benefits public class Location { /** The latitude value.*/ private double latitude; /** The longitude value.*/ private double longitude; } public List<BikeStation> findWithin(final Location[] corners) { return bikeStationCollection.find(s -> s.location.geoWithin(corners)) .toList(); } public class QBikeStation implements QueryMetadata<BikeStation> { @DocumentField(name="location") public LocationField location; ... } @Document(collection="bikestations") public class BikeStation { @DocumentField private Location location; ... } public interface LocationField { public boolean geoWithin(final Location[] corners); ... }

Lambda Expression Analysis (this is the fun part, really)

Lambda Expression Analysis @FunctionalInterface public interface FilterExpression<T> extends Predicate<T>, Serializable { } Step#1 : Use a Serializable Functional Interface

Lambda Expression Analysis public static <T> SerializedLambda getSerializedLambda( final FilterExpression<T> expression) { ... final Class<?> cl = expression.getClass(); final Method m = cl.getDeclaredMethod("writeReplace"); m.setAccessible(true); return (SerializedLambda) m.invoke(expression); ... } Step#2 : Locate the generated method

Lambda Expression Analysis Step#3 : read the generated bytecode Label L1125736023 VarInsn ALOAD #0 FieldInsn GETFIELD com/sample/QUser.firstName (desc=Lorg/lambdamatic/mongodb/metadata/StringField;) LdcInsn john MethodInsn INVOKEVIRTUAL java/lang/Object.equals (desc=(Ljava/lang/Object;)Z) JumpInsn IFEQ L1636182655 VarInsn ALOAD #0 FieldInsn GETFIELD com/sample/QUser.lastName (desc=Lorg/lambdamatic/mongodb/metadata/StringField;) Label L1122606666 LdcInsn doe MethodInsn INVOKEVIRTUAL java/lang/Object.equals (desc=(Ljava/lang/Object;)Z) JumpInsn IFNE L350068407 Label L1636182655 VarInsn ALOAD #0 FieldInsn GETFIELD com/sample/QUser.userName (desc=Lorg/lambdamatic/mongodb/metadata/StringField;) LdcInsn jdoe MethodInsn INVOKEVIRTUAL java/lang/Object.equals (desc=(Ljava/lang/Object;)Z) JumpInsn IFNE L350068407 Insn ICONST_0 JumpInsn GOTO L1820383114 Label L350068407 Insn ICONST_1 Label L1820383114 Insn IRETURN Label L369049246 LocalVariable u (desc=Lcom/sample/QUser;) index=0

Lambda Expression Analysis Step#4 : build an AST if(u.firstName.equals("john")) { if(u.lastName.equals("doe")) { return true } else { if(u.userName.equals("jdoe")) { return true } else { return false } } } else { if(u.userName.equals("jdoe")) { return true } else { return false } }

if(u.firstName.equals("john")) { if(u.lastName.equals("doe")) { return true } else { if(u.userName.equals("jdoe")) { return true } else { return false } } } else { if(u.userName.equals("jdoe")) { return true } else { return false } } if(u.firstName.equals("john")) { if(u.lastName.equals("doe")) { return true } else { if(u.userName.equals("jdoe")) { return true } else { return false } } } else { if(u.userName.equals("jdoe")) { return true } else { return false } (u.firstName.equals("john") && u.lastName.equals("doe")) || (u.firstName.equals("john") && !u.lastName.equals("doe") && u.userName.equals("jdoe")) || (!u.firstName.equals("john") && u.userName.equals("jdoe")) Lambda Expression Analysis Step#5 : Thin out the AST

(u.firstName.equals("john") && u.lastName.equals("doe")) || (u.firstName.equals("john") && !u.lastName.equals("doe") && u.userName.equals("jdoe")) || (!u.firstName.equals("john") && u.userName.equals("jdoe")) Lambda Expression Analysis Step#6 : Further simplify the AST (u.firstName.equals("john") && u.lastName.equals("doe")) || (u.firstName.equals("john") && !u.lastName.equals("doe") && u.userName.equals("jdoe")) || (!u.firstName.equals("john") && u.userName.equals("jdoe"))

Lambda Expression Analysis Boolean algebra to the rescue ! a.(b.c) = a.b.c a + (b + c) = a + b + c a.(!a + b).(!a + c) = a.b.c a + (!a.b) + (!a.c) = a + b + c a.(a + b).(a + c) = a a + (a.b) + (a.c) = a (a.b) + (a.c) + (a.d) = a.(b + c + d) (a + b).(a + c).(a + d) = a + (b.c.d) a + a = a a.a = a a.!a = O a + !a = I O + a = a O.a = O 1 + a = 1 1.a = a a.(b + c + d) = (a.b) + (a.c) + (a.d) a + (b.c.d) = (a + b).(a + c).(a + d)

Lambda Expression Analysis Step#6 : further simplify the statement tree (u.firstName.equals("john") && u.lastName.equals("doe")) || (u.firstName.equals("john") && !u.lastName.equals("doe") && u.userName.equals("jdoe")) || (!u.firstName.equals("john") && u.userName.equals("jdoe")) (u.firstName.equals("john") && u.lastName.equals("doe")) || u.userName.equals("jdoe")

Performances ? • Byte code is analyzed on ﬁrst access to Lambda Expression ( <100ms) • "Raw" AST is cached for subsequent calls • Placeholders in AST for captured arguments

Part II. Managing data on MongoDB

Managing Data on MongoDB • Providing Codecs for Lambda Expressions and Documents • Skipping the "DBObject" DTOs layer MongoDB Java Driver Integration

Querying MongoDB Service Layer Lambda Expression MongoDB Java Driver BSON Document MongoDB FilterExpression Codec BSON Document Domain object(s) Document Codec

Three more things (yes, three)

Query on Arrays final List<BlogEntry> blogEntries = blogEntryCollection.filter( e -> e.comments.elementMatch( c -> c.author.equals("anonymous") && c.date.greaterOrEquals(twoDaysAgo))) .toList(); final List<BlogEntry> blogEntries = blogEntryCollection.filter( e -> e.comments.author.equals("anonymous") &&   e.comments.date.greaterOrEquals(twoDaysAgo)) .toList();

Query Projection Projection Metadata class generation @Generated(value="o.l.m.a.DocumentAnnotationProcessor") public abstract class PBlogEntry implements ProjectionMetadata<BlogEntry> { @DocumentField(name="_id") public ProjectionField id; @DocumentField(name="authorName") public ProjectionField authorName; @DocumentField(name="publishDate") public ProjectionField publishDate; ... } @Document(collection="blog") public class BlogEntry { @DocumentId private String id; @DocumentField private String authorName; private Date publishDate; ... }

Query Projection import static org.lambdamatic.mongodb.Projection.include; final BlogEntry blogEntry = blogEntries.filter(e -> e.id.equals("1")) .projection(e -> include(e.authorName, e.title, e.publishDate)) .first(); @Generated(value="o.l.m.a.DocumentAnnotationProcessor") public abstract class PBlogEntry implements ProjectionMetadata<BlogEntry> { @DocumentField(name="_id") public ProjectionField id; @DocumentField(name="authorName") public ProjectionField authorName; @DocumentField(name="publishDate") public ProjectionField publishDate; ... } public interface Projection { @IncludeFields public static void include(final ProjectionField... fields) {} @ExcludeFields public static void exclude(final ProjectionField... fields) {} }

Query Projection Projecting array elements final BlogEntry blogEntry = blogEntryCollection.filter(e -> e.id.equals("1")) .projection(e -> include(e.authorName, e.title, e.publishDate, e.comments.elementMatch(c -> c.author.equals("anonymous") && c.date.greaterOrEquals(twoDaysAgo)))) .first();

Update Operations @Document(collection="blog") public class BlogEntry { @DocumentId private String id; /** Name of author of the blog entry. */ private String authorName; /** Title of the Blog Entry */ private String title; /** list of comments. */ private List<BlogEntryComment> comments; ... } Update Metadata class generation @Generated(value="o.l.m.a.DocumentAnnotationProcessor") public abstract class UBlogEntry implements UpdateMetadata<BlogEntry> { @DocumentField(name="_id") public String id; @DocumentField(name="authorName") public String authorName; @DocumentField(name="title") public String title; @DocumentField(name="comments") public UBlogEntryCommentArray comments; ... }

Update Operations BlogEntryComment comment = ... ; blogEntries.filter(e -> e.id.equals("1")). forEach(e -> { e.lastUpdate = new Date(); e.commentsNumber++; e.comments.push(comment);}); @Document(collection="blog") public class BlogEntry { @DocumentId private String id; /** date of last update. */ private Date lastUpdate; /** Number of comments */ private int commentsNumber; /** list of comments. */ private List<BlogEntryComment> comments; @EmbeddedDocument public class BlogEntryComment { /** comment author. */ private String author; /** comment date. */ private Date date; /** comment content. */ private String content;

Demo #2 Filter with projections and Update

Project Info http://github.com/lambdamatic • Give it a try ! • Clone it / Fork it / Star it • Open issues to discuss about API and features

DevNation'15 - Using Lambda Expressions to Query a Datastore

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DevNation'15 - Using Lambda Expressions to Query a Datastore