7.4.4.2.6. ClassBridge
有时,组合给定实体的多个属性并以特定的方式将此组合索引到 Lucene 索引中很有用。@ClassBridge 和 @ClassBridges 注释可以在类级别上定义,而非属性级别。在本例中,自定义字段网桥实施接收实体实例作为 value 参数,而不是特定属性。虽然如下例中未显示,但 @ClassBridge 支持 Basic Mapping 部分中讨论的 termVector 属性。
示例:实施类桥接
@Entity
@Indexed
(name="branchnetwork",
store=Store.YES,
impl = CatFieldsClassBridge.class,
params = @Parameter( name="sepChar", value=" " ) )
public class Department {
private int id;
private String network;
private String branchHead;
private String branch;
private Integer maxEmployees
...
}
public class CatFieldsClassBridge implements FieldBridge, ParameterizedBridge {
private String sepChar;
public void setParameterValues(Map parameters) {
this.sepChar = (String) parameters.get( "sepChar" );
}
public void set( String name, Object value, Document document, LuceneOptions luceneOptions) {
// In this particular class the name of the new field was passed
// from the name field of the ClassBridge Annotation. This is not
// a requirement. It just works that way in this instance. The
// actual name could be supplied by hard coding it below.
Department dep = (Department) value;
String fieldValue1 = dep.getBranch();
if ( fieldValue1 == null ) {
fieldValue1 = "";
}
String fieldValue2 = dep.getNetwork();
if ( fieldValue2 == null ) {
fieldValue2 = "";
}
String fieldValue = fieldValue1 + sepChar + fieldValue2;
Field field = new Field( name, fieldValue, luceneOptions.getStore(),
luceneOptions.getIndex(), luceneOptions.getTermVector() );
field.setBoost( luceneOptions.getBoost() );
document.add( field );
}
}
在本例中,特定的 CatFieldsClassBridge 应用到 部门 实例,字段桥接随后串联分支和网络,并索引串联。