The Hibernate type (Web hosts) system type depends on the
The Hibernate type system type depends on the dialect; for example, in PostgreSQL, the SQL type is BYTEA, and in Oracle it s RAW.) If a property in your persistent Java class is of type java.lang.String, Hibernate can map it to an SQL CLOB column, with the text mapping type. Note that in both cases, Hibernate initializes the property value right away, when the entity instance that holds the property variable is loaded. This is incon venient when you have to deal with potentially large values. One solution is lazy loading through interception of field access, on demand. However, this approach requires bytecode instrumentation of your persistent classes for the injection of extra code. We ll discuss lazy loading through bytecode instrumentation and interception in chapter 13, section 13.1.6, Lazy loading with interception. A second solution is a different kind of property in your Java class. JDBC supports locator objects (LOBs) directly.1 If your Java property is of type java.sql.Clob or java.sql.Blob, you can map it with the clob or blob mapping type to get lazy loading of large values without bytecode instrumentation. When the owner of the property is loaded, the property value is a locator object effectively, a pointer to the real value that isn t yet materialized. Once you access the property, the value is materialized. This on-demand loading works only as long as the database transaction is open, so you need to access any property of such a type when the owning entity instance is in a persistent and transactional state, not in detached state. Your domain model is now also bound to JDBC, because the import of the java.sql package is required. Although domain model classes are executable in isolated unit tests, you can t access LOB properties without a database connection. Mapping properties with potentially large values is slightly different if you rely on Java Persistence annotations. By default, a property of type java.lang.String is mapped to an SQL VARCHAR column (or equivalent, depending on the SQL dialect). If you want to map a java.lang.String, char[], Character[], or even a java.sql.Clob typed property to a CLOB column, you need to map it with the @Lob annotation: @Lob @Column(name = “ITEM_DESCRIPTION”) private String description; 1 Jim Starkey, who came up with the idea of LOBs, says that the terms BLOB and CLOB don t mean anything but were created by the marketing department. You can interpret them any way you like. We prefer locator objects, as a hint that they work like pointers.
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