sqlGrammerexception:无法在em.persist()上获得结果集

Question

我正在学习jpa，并逐渐降低了用jpa在我的桌子上创建一个新的条目，级联的孩子元素。

该代码正常工作，直到我想坚持一个新的条目。我最初认为这是一个映射错误，但我在数据库结构中没有发现任何错误(或者我是热量的BC(

那么为什么我不能坚持呢？

客户端

package client;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import dao.GeneralDAO;
import entity.Artemis;
import entity.Welt;
public class client {
    public static void main(String[] args) {
        GeneralDAO artemis = new GeneralDAO("JPA_REAL", Artemis.class);
        System.out.println(artemis);
        GeneralDAO welt = new GeneralDAO("JPA_REAL", Welt.class);
        System.out.println(welt);
        System.out.println("Artemis Liste: " + artemis.list());
        System.out.println("Artems by PK: " + artemis.findByPrimaryKey(1));
        System.out.println("Welt by PK: " + welt.findByPrimaryKey(2));
        System.out.println("Welt Liste: " + welt.list());
        Collection<?> objs;
        Collection<?> objs1;
        objs = artemis.list();
        objs1 = welt.list();
        Artemis art1 = null;
        System.out.println("Field: " + artemis.getField());

  Artemis a2 = new Artemis("Zeus");
          Artemis a3 = new Artemis();
          a3.setName("Jupiter");
          List<Welt> a2_welt = new ArrayList<Welt>();
          a2_welt.add(new Welt("Earth"));
          a2_welt.add(new Welt("Mars"));
          a2.setWelts(a2_welt);
          artemis.store(a2);


        for (Object s : objs) {
            System.out.println("s=" + ((Artemis) s).getName());
            System.out.println("id=" + ((Artemis) s).getId());
            for (Welt w : ((Artemis) s).getWelts())
                System.out.println("w=" + w.getName());
        }
        artemis.close();
        welt.close();
    }
}

dao

package dao;
import java.lang.reflect.Field;
import java.util.Collection;
import javax.persistence.*;

public class GeneralDAO {
    EntityManager em;
    private Field[] field;
    private int primaryKeyIndex;

    private Class <?> clazz;
    public GeneralDAO(String PersistenceUnit, Class <?> clazz) {
    EntityManagerFactory emf = Persistence.createEntityManagerFactory(PersistenceUnit);
    em = emf.createEntityManager();
    this.clazz=clazz;   
    }

    public Field[] getField() {
        field = clazz.getDeclaredFields();
        return field;
    }
    public Collection <?> list(){
        String Statement = "Select q from " + clazz.getSimpleName() + " q";
        return em.createQuery(Statement).getResultList();
    }
    public Object findByPrimaryKey(int pk) {
        Object returnObject = em.find(clazz, pk);
        return returnObject;
    }
    public void store(Object s) {
        EntityTransaction ta = em.getTransaction();
        ta.begin();
        em.persist(s);
        ta.commit();
    }
    public void remove(int pk) {
        Object returnObject = em.find(clazz, pk);
        EntityTransaction ta = em.getTransaction();
        ta.begin();
        em.remove(returnObject);
        ta.commit();
    }
    public void close() {
        em.clear();
        em.close();

    }
    public void refresh(Object s) {
        em.refresh(s);
    }
    /*
     * public Collection <?> executeQuery() { System.out.println("Query Start");
     * Query Query = em.createQuery("Select e from Artemis e join e.id t");
     * List<Artemis> resultList = Query.getResultList(); for (Artemis s: resultList)
     * System.out.println(Artemis.getName() "+" Artemis.getWorld()); }
     */
}

Welt Entity

package entity;
import java.io.Serializable;
import javax.persistence.*;

/**
 * The persistent class for the WELT database table.
 * 
 */
@Entity
@NamedQuery(name="Welt.findAll", query="SELECT w FROM Welt w")
public class Welt implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue
    @Column(name="id")
    int id;
    @Column(name="name")
    private String name;
    //bi-directional many-to-one association to Artemis
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="fk_artemis")
    private Artemis artemis;
    public Welt() {
    }
    public Welt(int i, String string, int j) {
    }
    public Welt(int i, String string) {
    }
    public Welt(String string) {
    }
    public long getId() {
        return this.id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return this.name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Artemis getArtemis() {
        return this.artemis;
    }
    public void setArtemis(Artemis artemis) {
        this.artemis = artemis;
    }
}

Artemis Entity

package entity;
import java.io.Serializable;
import javax.persistence.*;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

/**
 * The persistent class for the ARTEMIS database table.
 * 
 */
@Entity
@NamedQuery(name="Artemis.findAll", query="SELECT a FROM Artemis a")
public class Artemis implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue
    @Column(name="id")
    private int id;
    @Column(name="name")
    private String name;
    //bi-directional many-to-one association to Welt
    @OneToMany(mappedBy="artemis", fetch=FetchType.LAZY, cascade=CascadeType.PERSIST)
    private List<Welt> welts = new ArrayList<Welt>();
    public Artemis() {
    }
    public Artemis(int id, String name) {
        this.id=id;
        this.name=name;
    }
    public Artemis(String name) {
        this.name=name;
    }
    public long getId() {
        return this.id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return this.name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public List<Welt> getWelts() {
        return welts;
    }
    public Collection<Welt> getWeltName() {
        return welts;
    }
    public void setWelts(List<Welt> welts) {
        this.welts = welts;
    }
    public Welt addWelt(Welt welt) {
        getWelts().add(welt);
        welt.setArtemis(this);
        return welt;
    }
    public Welt removeWelt(Welt welt) {
        getWelts().remove(welt);
        welt.setArtemis(null);
        return welt;
    }
    @Override
    public String toString() {
        return "Artemis [id=" + id + ", name=" + name + ", welts=" + welts + "]";
    }

}

stacktrace

//other console output
    dao.GeneralDAO@77c1e611
    Artemis Liste: []
    Artems by PK: null
    Welt by PK: null
    Welt Liste: []
    Field: [Ljava.lang.reflect.Field;@17fede14
    Juni 27, 2019 9:06:16 NACHM. org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
    WARN: SQL Error: 2289, SQLState: 42000
    Juni 27, 2019 9:06:16 NACHM. org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
    ERROR: ORA-02289: sequence does not exist
    Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
        at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:154)
        at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181)
        at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:188)
        at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811)
        at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789)
        at dao.GeneralDAO.store(GeneralDAO.java:46)
        at client.client.main(client.java:77)
    Caused by: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
        at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:63)
        at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
        at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:113)
        at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:99)
        at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:69)
        at org.hibernate.id.enhanced.SequenceStructure$1.getNextValue(SequenceStructure.java:95)
        at org.hibernate.id.enhanced.NoopOptimizer.generate(NoopOptimizer.java:40)
        at org.hibernate.id.enhanced.SequenceStyleGenerator.generate(SequenceStyleGenerator.java:519)
        at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:119)
        at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:192)
        at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135)
        at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:62)
        at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804)
        ... 3 more
    Caused by: java.sql.SQLSyntaxErrorException: ORA-02289: sequence does not exist
        at oracle.jdbc.driver.T4CTTIoer11.processError(T4CTTIoer11.java:494)
        at oracle.jdbc.driver.T4CTTIoer11.processError(T4CTTIoer11.java:446)
        at oracle.jdbc.driver.T4C8Oall.processError(T4C8Oall.java:1052)
        at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:537)
        at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:255)
        at oracle.jdbc.driver.T4C8Oall.doOALL(T4C8Oall.java:610)
        at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:253)
        at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:86)
        at oracle.jdbc.driver.T4CPreparedStatement.executeForDescribe(T4CPreparedStatement.java:765)
        at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:921)
        at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1099)
        at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3640)
        at oracle.jdbc.driver.T4CPreparedStatement.executeInternal(T4CPreparedStatement.java:1384)
        at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:3687)
        at oracle.jdbc.driver.OraclePreparedStatementWrapper.executeQuery(OraclePreparedStatementWrapper.java:1165)
        at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:60)
        ... 11 more
    Caused by: Error : 2289, Position : 7, Sql = select hibernate_sequence.nextval from dual, OriginalSql = select hibernate_sequence.nextval from dual, Error Msg = ORA-02289: sequence does not exist
        at oracle.jdbc.driver.T4CTTIoer11.processError(T4CTTIoer11.java:498)
        ... 26 more

Answer 1

@joincolumn注释指定列的名称被用作目标实体上的外键。

在上面的Welt类中，联接列的名称设置为" FK_ARTEMIS"。

@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="fk_artemis")
private Artemis artemis;

因此，如果产品表上的外键被命名以外的其他内容，则通常会出现此错误。

您需要更改表上的列名或您在@joincolumn中使用的名称，以使其匹配。

此错误有更多原因。但是，主要是由于名称不匹配。

Answer 2

失败的原因是我的数据库没有 @generated value

中使用的序列

sidenote：如果我会丢下@generatedValue并与 主键(1，"任何"(它将起作用。

@generatedValue在Oracle中使用标准序列，但我没有生成一个。我用create sequence ...为每个表制作了两个序列，并用typ修改了@generatedValue，序列的名称和添加@SequenceGenerator。

我不得不删除使用drop sequence dual和自动生成密钥，持久和外键的序列。