OJB中的多表查询和更新

文章作者 100test 发表时间 2007:03:14 16:47:02
来源 100Test.Com百考试题网

OJB的文章实在是少的可怜，自己总结了一下一些重点的内容。想到哪里写到哪里吧

比如有课程(event)和类别(catalog)两张表，二者是多对多的关系，关系表叫做catalogEventBridge，字段为[catalogID,eventID]，现在要做的是一旦查询出一个catalog，就要把相关的event也全部搜索出来。


1.repository_user.xml中作如下定义：




primarykey="true" /> jdbc-type="VARCHAR" /> class-ref="org.pie.vls.Catalog.CatalogEventBridge" auto-retrieve="true" auto-
0update="true" auto-0delete="true">
class="org.pie.vls.Catalog.CatalogEventBridge" table="catalogEventBridge">
primarykey="true" /> jdbc-type="INTEGER" primarykey="true" /> class="org.pie.vls.EventType.EventType" table="eventType" > name="eventTypeID" column="eventTypeID" jdbc-type="INTEGER" primarykey="true"
autoincrement="true" />

name="eventTypeTitle"
column="eventTypeTitle"
jdbc-type="VARCHAR"
/>
... ...




2. bean文件的定义



EventType.java


public class EventType implements Cloneable, Comparable {
private String eventTypeTitle.
private String eventTypeCode.
private String eventTypeDesc.
private int eventTypeID.
public int getEventTypeID() {
return this.eventTypeID.
}

public void setEventTypeID(int value) {
this.eventTypeID = value.
}
... ...
}



catalog.java


public class Catalog implements Comparable {

private int catalogID.
private String catalogName = "".
private List catalogEventList = new Vector().
/**
* @return Returns the catalogID.
*/
public int getCatalogID() {
return catalogID.
}

/**
* @param catalogID The catalogID to set.
*/
public void setCatalogID(int catalogID) {
this.catalogID = catalogID.
}

/**
* @return Returns the catalogName.
*/
public String getCatalogName() {
return catalogName.
}

/**
* @param catalogName The catalogName to set.
*/
public void setCatalogName(String catalogName) {
this.catalogName = catalogName.
}

/**
* @return Returns the catalogEventList.
*/
public List getCatalogEventList() {
return catalogEventList.
}

/**
* @param catalogEventList The catalogEventList to set.
*/
public void setCatalogEventList(List catalogEventList) {
this.catalogEventList = catalogEventList.
}
}


CatalogEventBridge.java


public class CatalogEventBridge {
private int catalogID = 0.
private int eventTypeID = 0.
/**
* @return Returns the catalogID.
*/
public int getCatalogID() {
return catalogID.
}

/**
* @param catalogID The catalogID to set.
*/
public void setCatalogID(int catalogID) {
this.catalogID = catalogID.
}

/**
* @return Returns the eventTypeID.
*/
public int getEventTypeID() {
return eventTypeID.
}

/**
* @param eventTypeID The eventTypeID to set.
*/
public void setEventTypeID(int eventTypeID) {
this.eventTypeID = eventTypeID.
}
}



3. 定义DAO


import java.util.Collection.
import java.util.Iterator.

import org.apache.log4j.Logger.
import org.apache.ojb.broker.PersistenceBroker.
import org.apache.ojb.broker.PersistenceBrokerFactory.
import org.apache.ojb.broker.query.Criteria.
import org.apache.ojb.broker.query.QueryByCriteria.
import org.apache.ojb.broker.query.QueryFactory.
import org.odmg.Implementation.
import org.pie.vls.Application.AbstractVLSBase.

public class CatalogDAO extends AbstractVLSBase {

private Collection catalogList.
private PersistenceBroker broker.
private static final Logger logger = Logger.getLogger(Catalog.class).
private int catalogID = 0.

public CatalogDAO(Implementation impl) {
super(impl).
init().
}

public CatalogDAO(Implementation impl, int catalogID) {
super(impl).
this.catalogID = catalogID.
init().
}

/* (non-Javadoc)
* @see org.pie.vls.Application.VLSBase#init()
*/
public void init() {
// TODO Auto-generated method stub
try {
broker = PersistenceBrokerFactory.defaultPersistenceBroker().
broker.clearCache().

Criteria crit = new Criteria().
if (this.catalogID > 0) {
crit.addEqualTo("catalogID", new Integer(this.catalogID)).
}

QueryByCriteria tquery = QueryFactory.newQuery(Catalog.class, crit).
this.catalogList = broker.getCollectionByQuery(tquery).
broker.clearCache().
broker.close().
} catch (Throwable t) {
logger.error(t.getMessage(), t).
}
}

public boolean isEmpty(){
return this.catalogList.isEmpty().
}

public Collection getCatalogList() {
return this.catalogList.
}

public Catalog getCatalog() {
Iterator iter = this.catalogList.iterator().
Catalog catalog = (Catalog) iter.next().
return catalog.
}

public void create(Catalog catalog) {
0update(catalog).
}

public void 0update(Catalog catalog) {
try {
broker = PersistenceBrokerFactory.defaultPersistenceBroker().
broker.clearCache().
broker.beginTransaction().
broker.store(catalog).
broker.commitTransaction().
broker.close().
} catch (Throwable t) {
logger.error(t.getMessage(), t).
}
}

public void 0delete(Catalog catalog) {
try {
broker = PersistenceBrokerFactory.defaultPersistenceBroker().
broker.clearCache().
broker.beginTransaction().
broker.0delete(catalog).
broker.commitTransaction().
broker.close().
} catch (Throwable t) {
logger.error(t.getMessage(), t).
}
}
}

catalogEventBridgeDAO.java和eventTypeDAO.java跟上面的这个DAO类似，就不再重复。

使用方法就很简单了，只要通过CatalogDAO得到了一个catalog的实例，那么就可以通过catalog.getCatalogEventList()来获得bridge表中相关的数据，同样，调用catalogDAO中的create,0update和0delete方法，不仅对catalog表作操作，同样也对catalogEventBridge表中的数据作操作。