如何在hibernate.cfg.xml中連接postgresql

Question

我試圖通過hibernate將一些數據插入到postgresql中。 但是，沒有太多關於使用postgresql配置hibernate的教程（我知道，它應該類似於mysql =））

SRC /主/資源/ hibernate.cfg.xml中

<hibernate-configuration>
<session-factory>
<property name="connection.driver_class">org.postgresql.Driver</property>
<property name="connection.url">jdbc:postgresql://127.0.0.1:5432/myDatabase</property>
<property name="connection.username">myUser</property>
<property name="connection.password">myPassword</property>

<!-- JDBC connection pool (use the build-in) -->
<property name="connection.pool_size">1</property>
<!-- SQL dialect -->
<property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>
<property name="cache.provider_class">org.hibernate.cache.HashtableCacheProvider</property>
<property name="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>

<!-- thread is the short name for org.hibernate.context.ThreadLocalSessionContext -->
<property name="current_session_context_class">thread</property>

<!-- Set "true" to show SQL statements -->
<property name="hibernate.show_sql">true</property>

<!-- mapping class using annotation -->
<mapping class="com.hib.entities.Student"></mapping>
</session-factory>

</hibernate-configuration>

的src /主/爪哇/

package com.hib.init;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class Hibernateutil {
private static final SessionFactory sessionF;
private static final ServiceRegistry serviceR;

static {
    Configuration conf = new Configuration();
    conf.configure();
    System.out.println("Begin");
    serviceR = new ServiceRegistryBuilder().applySettings(conf.getProperties()).buildServiceRegistry();
    System.out.println("Ready???");
    try {
        sessionF = conf.buildSessionFactory(serviceR);
        System.out.println("Success??");
    }catch(Exception e) {
        throw new ExceptionInInitializerError(e);
    }
}

public static SessionFactory getSeeionFactory() {
    return sessionF;
}
}

src / main / java包com.hib.entities;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table
public class Student {

@Id
@GeneratedValue
private Integer id;
private String firstName;

private Integer age;

public Student() {}

public Student(Integer id, String firstName, Integer age) {
    super();
    this.id = id;
    this.firstName = firstName;
    this.age = age;
}

public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

public String getFirstName() {
    return firstName;
}

public void setFirstName(String firstName) {
    this.firstName = firstName;
}

public Integer getAge() {
    return age;
}

public void setAge(Integer age) {
    this.age = age;
}   
}

的src /主/ JAVA

package com.hib.demo;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import com.hib.entities.Student;
import com.hib.init.Hibernateutil;

public class DemoFirst {

public static void main(String[] args) {
    SessionFactory sessionFactory = Hibernateutil.getSeeionFactory();
    Session session = sessionFactory.openSession();
    session.beginTransaction();

    Student student = new Student();
    student.setFirstName("Bob");
    student.setAge(26);

    session.save(student);
    session.getTransaction().commit();

    session.close();
}
}

這是我得到的錯誤：

Success??
Hibernate: select nextval ('hibernate_sequence')
Aug 12, 2014 11:01:10 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 0, SQLState: 42P01
Aug 12, 2014 11:01:10 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: ERROR: relation "hibernate_sequence" does not exist
Position: 17
Exception in thread "main" org.hibernate.exception.SQLGrammarException: ERROR: relation        "hibernate_sequence" does not exist
Position: 17
at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:122)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:47)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:129)
at org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(AbstractProxyHandler.java:81)
at com.sun.proxy.$Proxy9.executeQuery(Unknown Source)
at org.hibernate.id.SequenceGenerator.generateHolder(SequenceGenerator.java:123)
at org.hibernate.id.SequenceGenerator.generate(SequenceGenerator.java:116)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:120)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:204)
at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:55)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:189)
at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:49)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:642)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:635)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:631)
at com.hib.demo.DemoFirst.main(DemoFirst.java:20)


Caused by: org.postgresql.util.PSQLException: ERROR: relation "hibernate_sequence" does not exist
Position: 17
at    org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2062)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1795)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:479)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:367)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:271)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:122)
... 14 more

的pom.xml

 <dependency>
    <groupId>postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <version>8.4-701.jdbc4</version>
</dependency>

Answer 1

根據此主題，您必須按如下方式設置Id注釋：

@GeneratedValue(strategy = GenerationType.IDENTITY)

Answer 2

您忘了添加DDL自動生成屬性。 您可以使用以下任何設置：

<property name="hibernate.hbm2ddl.auto" value="update">
<property name="hibernate.hbm2ddl.auto" value="create">
<property name="hibernate.hbm2ddl.auto" value="create-drop">

1. update將創建然后只是更新DDL架構
2. 創造是要創建模式，如果它不存在
3. create-drop將在SessionFactory初始化時創建模式，並在SessionFactory被銷毀時銷毀它。 這在集成測試期間很有用。

Answer 3

您應該映射beetwen table-entity class，column-field。 例如（表和列應該存在）：

@Entity
@Table(name = "student")
public class Student {

@Id
@GeneratedValue
@Column(name = "id")
private Integer id;

@Column(name = "first_name")
private String firstName;

@Column(name = "age")
private Integer age;

Answer 4

因為您使用的是@GeneratedValue（）

它將查找您使用的數據庫如何生成ID。 對於MySql或HSQSL，有增量字段自動遞增。 在Postgres或Oracle中，它們使用序列表。 由於您沒有指定序列表名稱，因此它將查找名為hibernate_sequence的序列表並將其用作默認值。 所以你可能在數據庫中沒有這樣的序列表，現在你得到了那個錯誤。

要么添加一個hibernate_sequence

@GeneratedValue(strategy=SEQUENCE)

或者您自己的序列表，並使用注釋命名您喜歡的序列表

@GeneratedValue(strategy=SEQUENCE, generator="student_id_seq") 

希望有所幫助

Answer 5

通過Hibernate連接到Postgresql - > hibernate.cfg.xml中的配置將是：

<session-factory>

    <!-- SQL dialect -->
    <!-- <property name="dialect">org.hibernate.dialect.H2Dialect</property> -->

    <!-- Database connection settings -->

    <property name="hibernate.connection.driver_class">org.postgresql.Driver</property>
    <property name="connection.url">jdbc:postgresql://localhost:5432/db_name</property>
    <property name="connection.username">username</property>
    <property name="connection.password">db_assword</property>

    <!-- JDBC connection pool (use the built-in) -->
    <property name="connection.pool_size">1</property>


    <!-- Disable the second-level cache -->
    <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

    <!-- Echo all executed SQL to stdout -->
    <property name="show_sql">true</property>

    <!-- Drop and re-create the database schema on startup -->
    <property name="hbm2ddl.auto">update</property>
    <!-- <property name="hbm2ddl.auto">validate</property> -->

    <!-- The mapping information of entities -->
    <!-- <mapping class="hibernate_example.envers.Book" /> -->
    <!-- <mapping class="hibernate_example.envers.Student" /> -->
    <!-- <mapping class="hibernate_example.envers.AuditEntity" /> -->


</session-factory>

Answer 6

你的id應該是這樣的：

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "my_id_gen")
@SequenceGenerator(name = "my_id_gen", sequenceName = "my_id_seq")
private Long id;

sequenceName屬性應該引用數據庫中的正確序列。 如果您將列創建為序列類型，那么它應該是tableName_columnName_seq。