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Java Persistence/Inheritance - Wikibooks, open books for an open world - 0 views

en.wikibooks.org/...Inheritance java jpa inheritance @Inheritance @MappedSuperclass
shared by kuni katsuya on 24 Sep 12 - No Cached
  • Inheritance
  • hardest part of persisting inheritance is choosing how to represent the inheritance in the database
  • There are three inheritance strategies defined from the InheritanceType enum,
  • ...101 more annotations...
  • SINGLE_TABLE
  • TABLE_PER_CLASS
  • JOINED
  • Single table inheritance is the default
  • @MappedSuperclass
  • @Inheritance
  • mapped superclass is
  • not a persistent class
  • but allow common mappings to be define for its subclasses
  • Single Table Inheritance
    • kuni katsuya
      kuni katsuya on 24 Sep 12
       
      implemented as a sparse table. ie. all attributes from all entities end up as columns in the 'super' table
  • single table is used to store all of the instances of the entire inheritance hierarchy
  • table will have a column for
  • every attribute
  • every class
  • in the hierarchy
  • discriminator column
  • is used to determine which class the particular row belongs to
  • abstract
  • Project
  • extends Project
  • extends Project
  • @DiscriminatorValue("S")
  • @DiscriminatorValue("L")
  • @DiscriminatorColumn(name="PROJ_TYPE")
  • @Inheritance
  • @Table(name="PROJECT")
  • single table inheritance
  • Joined, Multiple Table Inheritance
  • mirrors the object model in the data model
  • table is defined for each class in the inheritance hierarchy to store only the local attributes of that class
  • Each table in the hierarchy must also store the object's id (primary key), which is
  • only defined in the root class
  • share the same id attribute
  • joined inheritance
  • @Inheritance(strategy=
  • InheritanceType.JOINED
  • @DiscriminatorColumn(name="PROJ_TYPE")
  • @Table(name="PROJECT")
  • abstract
  • Project
  • @DiscriminatorValue("L")
  • @Table(name=
  • "LARGEPROJECT"
  • LargeProject
  • Project
  • @DiscriminatorValue("S")
  • @Table(name=
  • "SMALLPROJECT"
  • SmallProject
  • Project
  • Table Per Class Inheritance
  • Advanced
  • table is defined for
  • each concrete class
  • in the inheritance hierarchy to store
  • all the attributes
  • of that class and
  • all of its superclasses
  • table per class inheritance
  • @Inheritance(strategy=
  • InheritanceType.TABLE_PER_CLASS
  • abstract
  • Project
  • @Table(name="LARGEPROJECT")
  • LargeProject
  • Project
  • @Table(name="SMALLPROJECT")
  • SmallProject
  • Project
  • Mapped Superclasses
  • similar to table per class inheritance, but does not allow querying, persisting, or relationships to the superclass
  • mapped superclass
  • @MappedSuperclass
  • abstract
  • Project
  • @Column(name="NAME")
  • @Table(name="LARGEPROJECT")
  • LargeProject
  • Project
  • @AttributeOverride
  • "PROJECT_NAME"
  • "name"
  • @Table("SMALLPROJECT")
  • SmallProject
  • Project
  • cannot have a relationship to a mapped superclass
  • Joined, Multiple Table Inheritance
  • oined, Multiple Table Inheritance
  • abstract
  • abstract c
  • extends Project
  • Mapped Superclasses
  • Mapped Superclasses
  • apped Superclasses
  • allows inheritance to be used in the object model, when it does not exist in the data model
  • @MappedSuperclass
  • MappedSuperclass
  • abstract
  • abstract
  • extends Project
  • extends Project
22More

BlazeDS Developer Guide - 0 views

livedocs.adobe.com/...help.html graniteds flex java type conversion
shared by kuni katsuya on 01 Nov 12 - Cached
  • Serializing between ActionScript and Java
  • java.util.Date (formatted for Coordinated Universal Time (UTC))
  • java.util.Date, java.util.Calendar, java.sql.Timestamp, java.sql.Time, java.sql.Date
  • ...19 more annotations...
  • Object (generic)
  • java.util.Map
  • Array (dense)
  • java.util.List
  • List becomes ArrayList SortedSet becomes TreeSet Set becomes HashSet Collection becomes ArrayList
  • Array (sparse) java.util.Map java.util.Map
  • java.util.Map If a Map interface is specified, creates a new java.util.HashMap for java.util.Map and a new java.util.TreeMap for java.util.SortedMap.
  • BlazeDS passes an instance of java.util.ArrayList to parameters typed with the java.util.List interface and any other interface that extends java.util.Collection. Then these types are
  • sent back to the client as mx.collections.ArrayCollection instances
  • If you require normal ActionScript Arrays sent back to the client, you must set the legacy-collection element to true in the serialization section of a channel-definition's properties; for more information, see Configuring AMF serialization on a channel.
  • legacy-collection Default value is false. When true, instances of
  • java.util.Collection
  • are returned as
  • ActionScript Arrays
  • legacy-map Default value is false. When true, java.util.Map instances are serialized as an ECMA Array or associative array instead of an anonymous Object.
  • A typical reason to use custom serialization is to avoid passing all of the properties of either the client-side or server-side representation of an object across the network tier.
  • standard serialization scheme, all public properties are passed back and forth between the client and the server.
  • Explicitly mapping ActionScript and Java objects
  • Private properties, constants, static properties, and read-only properties, and so on, are not serialized
25More

Entity-attribute-value model - Wikipedia, the free encyclopedia - 0 views

en.wikipedia.org/...Entity-attribute-value_model eav sparse open schema
shared by kuni katsuya on 01 Jul 12 - Cached
  • Entity–attribute–value model
  • Entity–attribute–value model (EAV) is a data model to describe entities where the number of attributes (properties, parameters) that can be used to describe them is potentially vast, but the number that will actually apply to a given entity is relatively modest
  • also known as object–attribute–value model, vertical database model and open schema
  • ...21 more annotations...
  • In an EAV data model, each attribute-value pair is a fact describing an entity, and a row in an EAV table stores a single fact
  • EAV tables are often described as "long and skinny": "long" refers to the number of rows, "skinny" to the few columns
  • Data is recorded as three columns: The entity: the item being described. The attribute or parameter: a foreign key into a table of attribute definitions. At the very least, the attribute definitions table would contain the following columns: an attribute ID, attribute name, description, data type, and columns assisting input validation
  • The value of the attribute
  • Row modeling, where facts about something (in this case, a sales transaction) are recorded as multiple rows rather than multiple columns
  • differences between row modeling and EAV (which may be considered a generalization of row-modeling) are:
  • A row-modeled table is homogeneous in the facts that it describes
  • The data type of the value column/s in a row-modeled table is pre-determined by the nature of the facts it records. By contrast, in an EAV table, the conceptual data type of a value in a particular row depend on the attribute in that row
  • In the EAV table itself, this is just an attribute ID, a foreign key into an Attribute Definitions table
  • The Attribute
  • The Value
  • Coercing all values into strings
  • larger systems use separate EAV tables for each data type (including binary large objects, "BLOBS"), with the metadata for a given attribute identifying the EAV table in which its data will be stored
  • Where an EAV system is implemented through RDF, the RDF Schema language may conveniently be used to express such metadata
  • access to metadata must be restricted, and an audit trail of accesses and changes put into place to deal with situations where multiple individuals have metadata access
  • quality of the annotation and documentation within the metadata (i.e., the narrative/explanatory text in the descriptive columns of the metadata sub-schema) must be much higher, in order to facilitate understanding by various members of the development team.
  • Attribute metadata
  • Validation metadata include data type, range of permissible values or membership in a set of values, regular expression match, default value, and whether the value is permitted to be null
    • kuni katsuya
      kuni katsuya on 01 Jul 12
       
      jsr-299 bean validation anyone?  :)
  • Presentation metadata: how the attribute is to be displayed to the user
  • Grouping metadata: Attributes are typically presented as part of a higher-order group, e.g., a specialty-specific form. Grouping metadata includes information such as the order in which attributes are presented
  • Advanced validation metadata Dependency metadata:
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