Features
ContentsGeneral FeaturesJDO Features Database Integration Features JDBC Performance Features Developer Features Get StartedMain PageDownload User's Guide Tutorial Changelog Help OutDeveloper OverviewInternal JavaDocs Project Page |
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General FeaturesInterface-Based PersistenceXORM persists data corresponding to abstract methods and interface methods that follow standard Java bean naming conventions. For traditional data objects (objects without custom behavior), you can provide only a Java interface and let XORM do the work of implementing the class. No Compile-Time Enhancement or Source Code GenerationXORM does not require any preprocessing of source files or bytecode class files. This means no extra Ant tasks and messy development configuration details. JDO FeaturesJDO APIXORM uses the standard JDO 1.0 API. XORM-specific classes need only be referenced for factory methods to acquire new persistent object instances. Some JDO methods are not yet implemented. JDO Query LanguageXORM uses JDOQL as its default query mechanism, so developers can use a Java-like syntax, including Java class and field names. Some JDOQL features are not yet implemented. Reverse Engineering of JDO MetadataAn Ant task will read in all the classes and interfaces in a package and create a JDO metadata for you to add mapping information to. Database Integration FeaturesMapping to Existing TablesXORM is designed to integrate with an existing relational database. It does not create or require any special tables or columns. Mapping to Read-Only ColumnsXORM can be configured to treat certain database columns as read-only, ensuring that those columns will never be included in update or insert operations. One-To-Many MappingsXORM support mapping foreign keys to an object to create collections. Many-To-One MappingsXORM supports mapping object references to foreign key columns. Many-To-Many MappingsXORM supports using a join table for collection references. Reverse Engineering of Database Schema XMLXORM comes with Ant tasks to generate the required database schema XML file. This human-readable file can be edited by hand or regenerated to capture further updates to a schema. Integration with Primary Key GenerationXORM can use autoincrement facilities of SQL databases or sequences for primary key generation. JDBC Performance FeaturesUse of Prepared StatementsXORM uses JDBC Prepared Statements wherever possible, allowing JDBC drivers to optimize database access accordingly. Lazy Loading of Object InstancesXORM loads only the objects you need at runtime, subject to configurable default fetch group settings. By default, object references use lazy loading. If certain references are commonly traversed, you can indicate this in the JDO metadata file, and XORM will issue optimized SQL join or outer join queries to prefetch the data. Partial Loading of Object InstancesBased on settings in the JDO metadata, XORM will load by default only the fields of your objects that are specified. Access to other fields will cause additional SQL statements to be issued, but may improve performance for large data fields. Lazy Loading of CollectionsCollections are also lazy loaded by default. Optimized Size QueriesInvoking the size() method on a persistent object Collection will result in a SQL count(*) statement if the collection has not yet been loaded. Minimal Object UpdatesXORM will only update objects whose values change during a transaction, and will only update the particular columns of the database rows which change. Optimized Many-to-Many UpdatesXORM generates incremental updates to many-to-many mapping tables, instead of rewriting all entries for a given object whenever the collection changes. Factory-level Object CacheThe factory-level object cache is enabled by default. All data read from the database goes into the cache so that multiple lookups of the same object are reduced to a single SQL query. The cache can be disabled for applications with multiple instances writing to the database. Connection PoolingXORM has built in connection pooling that works with any JDBC driver. The pool can be configured to automatically check for bad connections and recover in many situations. Custom SQL QueriesXORM allows developers to use raw SQL in areas where queries cannot be expressed in JDOQL. Developer FeaturesExtensible Datastore SupportXORM's datatore architecture allows heterogeneous datastores to be accessed through a common API. Support for most standard SQL databases is usually trivial; support for custom storage APIs and integration with third-party products is straightforward. Customizable Fetch GroupsFetch groups that control which data will be prefetched can be determined at runtime by extending XORM's fetch group manager. Customizable Factory-Level Data CacheXORM's extensible cache API allows the default implementation, which uses SoftReferences, to be replaced or extended by other cache strategies. Extensible Query SupportXORM's query API allows developers to provide alternate query languages, including the possibility of object-oriented query techniques. |