我无法在查询中使用“包含”过滤器来理解JDO。 我使用的是在Google App Engine上的开发者页面上链接的blog entry。
当我用字符串列表查询时，每件事情都很有效......
String JDO：
Query q = pm.newQuery(
"select from Person where :p1.contains(favoriteFood) order by favoriteFood, age");
q.execute(Arrays.asList("Vogon Grandmothers", "Pie"));
但是当我尝试使用整数时，我会得到异常 ...
整数列表JDO：
Query q = pm.newQuery(
"select from Person where :p1.contains(favoriteNumber) order by favoriteNumber, age");
q.execute(Arrays.asList(42,99));
java.lang.ClassCastException：java.util.Arrays $ ArrayList无法强制转换为java.lang.Integer
整数数组JDO：
Query q = pm.newQuery(
"select from Person where :p1.contains(favoriteNumber) order by favoriteNumber, age");
q.execute(new Integer[]{42,99});
[Ljava.lang.Integer;无法转换为java.lang.Integer
更新所有GAE源文件
TestStuffServlet.java
package teststuff;
import java.io.IOException;
import java.util.Arrays;
import java.util.LinkedList;
import javax.servlet.http.*;
@SuppressWarnings("serial")
public class TestStuffServlet extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws IOException {
LinkedList<Person> personsWithFavoriteNumbers = Person.getPersonsWithFavoriteNumbers(Arrays.asList(1234));
resp.setContentType("application/json");
resp.getWriter().println(personsWithFavoriteNumbers);
}
}
Person.java
package teststuff;
import java.util.LinkedList;
import java.util.List;
import javax.jdo.PersistenceManager;
import javax.jdo.Query;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.Persistent;
@PersistenceCapable
public class Person {
@Persistent
private String name;
@Persistent
private Integer favoriteNumber;
public Person(String name, Integer favoriteNumber) {
this.name = name;
this.favoriteNumber = favoriteNumber;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getFavoriteNumber() {
return favoriteNumber;
}
public void setFavoriteNumber(Integer favoriteNumber) {
this.favoriteNumber = favoriteNumber;
}
public String toString(){
return this.name + " " + this.favoriteNumber.toString();
}
public static Boolean savePerson(Person personToSave) {
Boolean saveSuccessful = false;
PersistenceManager pm = PMF.get().getPersistenceManager();
try {
pm.makePersistent(personToSave);
saveSuccessful = true;
} finally {
pm.close();
}
return saveSuccessful;
}
public static LinkedList<Person> getPersonsWithFavoriteNumbers(List<Integer> favoriteNumbers) {
LinkedList<Person> personsWithFavoriteNumbers = new LinkedList<Person>();
PersistenceManager pm = PMF.get().getPersistenceManager();
Query q = pm.newQuery(Person.class);
q.setFilter(":p1.contains(favoriteNumber)");
try {
List<Person> results = (List<Person>) q.execute(favoriteNumbers);
//List<Person> results = (List<Person>) q.execute(new Integer[]{2,3333});
if (!results.isEmpty()) {
for (Person p : results) {
// Process result g
personsWithFavoriteNumbers.add(p);
}
} else {
// Handle "no results" case
}
} finally {
q.closeAll();
}
return personsWithFavoriteNumbers;
}
}
堆栈追踪
HTTP ERROR 500
访问/ teststuff时遇到问题。原因是：
java.util.Arrays$ArrayList cannot be cast to java.lang.Integer
Caused by:
java.lang.ClassCastException: java.util.Arrays$ArrayList cannot be cast to java.lang.Integer
at com.google.appengine.datanucleus.TypeConversionUtils$8.apply(TypeConversionUtils.java:161)
at com.google.appengine.datanucleus.TypeConversionUtils$8.apply(TypeConversionUtils.java:156)
at com.google.appengine.datanucleus.TypeConversionUtils.pojoValueToDatastoreValue(TypeConversionUtils.java:810)
at com.google.appengine.datanucleus.query.DatastoreQuery.addLeftPrimaryExpression(DatastoreQuery.java:1131)
at com.google.appengine.datanucleus.query.DatastoreQuery.handleContainsOperation(DatastoreQuery.java:969)
at com.google.appengine.datanucleus.query.DatastoreQuery.addExpression(DatastoreQuery.java:830)
at com.google.appengine.datanucleus.query.DatastoreQuery.addFilters(DatastoreQuery.java:739)
at com.google.appengine.datanucleus.query.DatastoreQuery.compile(DatastoreQuery.java:248)
at com.google.appengine.datanucleus.query.JDOQLQuery.performExecute(JDOQLQuery.java:158)
at org.datanucleus.store.query.Query.executeQuery(Query.java:1789)
at org.datanucleus.store.query.Query.executeWithArray(Query.java:1666)
at org.datanucleus.api.jdo.JDOQuery.execute(JDOQuery.java:243)
at teststuff.Person.getPersonsWithFavoriteNumbers(Person.java:66)
at teststuff.TestStuffServlet.doGet(TestStuffServlet.java:14)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:123)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:368)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:351)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:97)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:485)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)