我有这个实体类,称为"Pagina",我想根据对实体所做的更改来更新数据库中的条目.这不起作用.我没有错误,但数据库没有改变.
@Entity
@Table(name = "PAGINA")
@NamedQueries({@NamedQuery(name = "Pagina.findAll", query = "SELECT p FROM Pagina p"),
@NamedQuery(name = "Pagina.findHashByURL", query= "SELECT p.chash FROM Pagina p WHERE p.url = :url"),
@NamedQuery(name = "Pagina.findTimestampByURL", query= "SELECT p.timestamp FROM Pagina p WHERE p.url = :url"),
@NamedQuery(name = "Pagina.findByUrl", query = "SELECT p FROM Pagina p WHERE p.url = :url"),
@NamedQuery(name = "Pagina.findByProfondita", query = "SELECT p FROM Pagina p WHERE p.profondita = :profondita"),
@NamedQuery(name = "Pagina.findByIntervallo", query = "SELECT p FROM Pagina p WHERE …我需要排序一个指向struc的指针数组.实际上,我需要在地址之间进行搜索,以查看数组中是否存在指向结构的指定指针.不幸的是,我在这些结构中没有任何"可比性"的东西,所以我只想按地址排序.我的代码是这样的:
item* arr[SIZE];
//something is inserted
qsort(arr, SIZE, sizeof(item*), (void*)compare_funct);
//CUT
bsearch(curr, arr, SIZE, sizeof(item*), (void*)compare_funct);
我尝试创建一个compare_funct,只是将指针转换为int并返回它们的区别,但它似乎不起作用.特别是,当我进行bsearch时,即使我知道元素包含在数组中,我总是得到一个NULL作为返回值.
我一直在尝试在生成的Endpoint类中创建一些新方法,我发现了这种奇怪的行为:我可以在生成的类中添加一个方法,但我无法添加其中的两个,无论我添加哪两个.这是我生成的类的代码,我在其中添加了两个添加的方法的代码:
package it.raffaele.bills;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import javax.annotation.Nullable;
import javax.inject.Named;
import javax.jdo.PersistenceManager;
import javax.jdo.Query;
import javax.persistence.EntityExistsException;
import javax.persistence.EntityNotFoundException;
import com.google.api.server.spi.config.Api;
import com.google.api.server.spi.response.CollectionResponse;
import com.google.appengine.api.datastore.Cursor;
import com.google.appengine.datanucleus.query.JDOCursorHelper;
@Api(name = "utenteendpoint")
public class UtenteEndpoint {
/**
* This method lists all the entities inserted in datastore.
* It uses HTTP GET method and paging support.
*
* @return A CollectionResponse class containing the list of all entities
* persisted and a cursor to the next page.
*/
@SuppressWarnings({ "unchecked", …我在使用mysql的netbeans中使用JPA,我需要定义一个外键.我想以图形方式进行,因为使用netbeans 6.7 UI创建表非常容易,而无需处理SQL命令.你能告诉我怎么做吗？