问题
I used Hibernate 4.1.2 with Ehcache 2.4.3 (shipped together with hibernate when donwloaded hibernate).
My hibernate.cfg.xml :
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class"> com.microsoft.sqlserver.jdbc.SQLServerDriver </property>
<property name="hibernate.connection.url"> jdbc:sqlserver://localhost:1433;databaseName=Stock_indices</property>
<property name="hibernate.connection.username">xxx</property>
<property name="hibernate.connection.password">xxx</property>
<property name="hibernate.show_sql">true</property>
<property name="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</property>
<property name="hibernate.hbm2ddl.auto">update</property>
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">20</property>
<property name="hibernate.c3p0.timeout">300</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.idle_test_period">30</property>
<property name="hibernate.cache.use_second_level_cache">true</property>
<property name="hibernate.cache.use_query_cache">true</property>
<property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.SingletonEhCacheRegionFactory </property>
<property name="net.sf.ehcache.configurationResourceName">ehcache-entity.xml</property>
<mapping resource="mapping.xml"/>
</session-factory>
</hibernate-configuration>
ehcache-entity.xml :
<?xml version="1.0" encoding="UTF-8"?>
<ehcache>
<cache name="stockdata.StockDatabaseConnection" eternal="false"
maxElementsInMemory="5" overflowToDisk="true" diskPersistent="false"
timeToIdleSeconds="0" timeToLiveSeconds="300"
memoryStoreEvictionPolicy="LRU" />
</ehcache>
mapping.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="stockdata">
<class name="StockDatabaseConnection" table="STOCKINDEX">
<cache usage="read-only" />
<composite-id name="CompositeIDConnection">
<key-property name="ticker" column="TICKER"/>
<key-property name="indexdate" column="INDEXDATE"/>
</composite-id>
<property name="openprice"> <column name="OPENPRICE" /> </property>
<property name="closingprice"> <column name="CLOSEPRICE" /> </property>
<property name="highestprice"> <column name="HIGHPRICE" /> </property>
<property name="lowestprice"> <column name="LOWPRICE" /> </property>
<property name="volume"> <column name="VOLUME" /> </property>
</class>
</hibernate-mapping>
However, I got this exception :
java.lang.NullPointerException at org.hibernate.cache.ehcache.internal.util.HibernateUtil.loadAndCorrectConfiguration(HibernateUtil.java:64)
at org.hibernate.cache.ehcache.SingletonEhCacheRegionFactory.start(SingletonEhCacheRegionFactory.java:91)
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:281)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1741)
............
It seems that hibernate can not load configuration? How can I solve the problem? (The serlvet works fine without using Ehcache).
My servlet class :
package stockdataservlet;
import java.io.IOException;
import java.math.BigDecimal;
import java.util.Iterator;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import com.google.gson.Gson;
import com.microsoft.sqlserver.jdbc.*;
public class DataServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public static SessionFactory sessionfactory = null;
public void init() {
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
Configuration conf = new Configuration();
conf.configure();
ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(conf.getProperties()).buildServiceRegistry();
sessionfactory = conf.buildSessionFactory(serviceRegistry);
}
catch(Exception e){
e.printStackTrace();
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) {
Session session = null;
try{
session = sessionfactory.openSession();
Transaction transaction = session.beginTransaction();
Query query = session.createSQLQuery("SELECT * FROM STOCKINDEX WHERE TICKER = :index ").addScalar("CLOSEPRICE");
query.setParameter("index", "AAA");
List list = query.list();
transaction.commit();
String json = new Gson().toJson(list);
/*response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
response.getWriter().write(json);*/
}
catch(Exception e){
e.printStackTrace();
}
finally{
session.close();
}
}
}
回答1:
That's allright. You do not have to explicitly specify value for property "net.sf.ehcache.configurationResourceName" if the resource is named ehcache.xml and placed in a class path. You can chose this option when you have multiple cache managers.
Or you can just move all your resource files from lib to a directory like WEB-INF/resources so that it becomes easier to reference it under classpath.
Ehcache looks for a file called ehcache.xml in the top level of the classpath. Failing that it looks for ehcache-failsafe.xml in the classpath. ehcache-failsafe.xml is packaged in the Ehcache jar and should always be found.
回答2:
Finally I found the reason why my code didn't work. Thanks for Vinodn for your suggestion.
config.getDefaultCacheConfiguration().isTerracottaClustered()
Actually, I didn't configure defaultCache tag in my ehcache-entity.xml, as a result
config.getDefaultCacheConfiguration()
return null. So adding defaultCache solved the problem.
回答3:
Place ehcache-entity.xml in your classpath to be loaded by your hibernate configuration.
回答4:
adding defaultCache configuration in ehcache.xml help me too.
来源：https://stackoverflow.com/questions/10266359/java-lang-nullpointerexception-hibernate-used-with-ehcache