java如何使hibernate仅在表不存在的情况下创建表？

Question

如何使hibernate仅在表不存在的情况下创建表？我刚刚将“hibernate.hbm2ddl.auto”设置为“update”，但在重新启动服务器时出现了错误——错误就像“关系已经存在”

我的坚持。xml:-

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
         version="2.0">
<persistence-unit name="com.adwork">
    <description>Adwork</description>
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <!-- <class>com.mkyong.bean.User</class>  -->
    <properties>
        <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/>
        <property name="hibernate.hbm2ddl.auto" value="update"/>
        <property name="show_sql" value="true"/>
        <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false"/>

        <property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver"/>
        <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://localhost:5432/adwork"/>
        <property name="javax.persistence.jdbc.user" value="root"/>
        <property name="javax.persistence.jdbc.password" value="root"/>
    </properties>
</persistence-unit>

请帮忙。谢谢

以下是错误：-

ERROR: org.springframework.web.context.ContextLoader - Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'applicationStartUp' defined in ServletContext resource [/WEB-INF/spring/root-context.xml]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: com.adwork] Unable to build Hibernate SessionFactory
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1578)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:775)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:861)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:444)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:326)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4727)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5189)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:724)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:700)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:734)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:596)
at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1805)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: com.adwork] Unable to build Hibernate SessionFactory
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:877)
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:805)
at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:58)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
at com.adwork.survey.config.ApplicationStartUp.initIt(ApplicationStartUp.java:27)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeCustomInitMethod(AbstractAutowireCapableBeanFactory.java:1706)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1645)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574)
... 25 more
Caused by: org.hibernate.tool.schema.spi.SchemaManagementException: Unable to execute schema management to JDBC target [alter table person add column createdDate timestamp not null]
at org.hibernate.tool.schema.internal.TargetDatabaseImpl.accept(TargetDatabaseImpl.java:59)
at org.hibernate.tool.schema.internal.SchemaMigratorImpl.applySqlString(SchemaMigratorImpl.java:420)
at org.hibernate.tool.schema.internal.SchemaMigratorImpl.applySqlStrings(SchemaMigratorImpl.java:438)
at org.hibernate.tool.schema.internal.SchemaMigratorImpl.migrateTable(SchemaMigratorImpl.java:247)
at org.hibernate.tool.schema.internal.SchemaMigratorImpl.doMigrationToTargets(SchemaMigratorImpl.java:170)
at org.hibernate.tool.schema.internal.SchemaMigratorImpl.doMigration(SchemaMigratorImpl.java:60)
at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:129)
at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:97)
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:481)
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:444)
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:802)
... 36 more
Caused by: org.postgresql.util.PSQLException: ERROR: column "createddate" of relation "person" already exists
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2270)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1998)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:255)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:570)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:406)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeUpdate(AbstractJdbc2Statement.java:334)
at org.hibernate.tool.schema.internal.TargetDatabaseImpl.accept(TargetDatabaseImpl.java:56)
... 46 more

我的域类：-

@Entity
@Table(name = "person")
public class Person implements Serializable
{
/**
 * 
 */
private static final long serialVersionUID = 5129388836708407722L;

@Id
private Long id;

@OneToOne
@JoinColumn(name = "userId")
private Users user;

@Column(name = "firstName",nullable = false)
private String firstName;

@Column(name = "middleName",nullable = false)
private String middleName;

@Column(name = "lastName",nullable = false)
private String lastName;

@Column(name = "gender",nullable = false)
private String gender;

@Column(name = "dateOfBirth",nullable = false)
private Date dateOfBirth;

@Column(name = "age",nullable = false)
private Byte age;

@Column(name = "createdDate",nullable = false)
private Timestamp createdDate;

@Column(name = "lastUpdatedDate",nullable = false)
private Timestamp lastUpdateDate;

public Person() 
{
    // TODO Auto-generated constructor stub
}
//and setters / getters 
}

DB创建表脚本：-

CREATE TABLE person
(
  id bigint NOT NULL,
  age smallint NOT NULL,
  createddate timestamp without time zone NOT NULL,
  dateofbirth date NOT NULL,
  firstname character varying(255) NOT NULL,
  gender character varying(255) NOT NULL,
  lastname character varying(255) NOT NULL,
  lastupdateddate timestamp without time zone NOT NULL,
  middlename character varying(255) NOT NULL,
  userid bigint,
  CONSTRAINT person_pkey PRIMARY KEY (id),
  CONSTRAINT fkd8ja1o2m8k25sf0mxvhu4c0ti FOREIGN KEY (userid)
  REFERENCES users (user_id) MATCH SIMPLE
  ON UPDATE NO ACTION ON DELETE NO ACTION
)
WITH (
  OIDS=FALSE
);
ALTER TABLE person
  OWNER TO root;

列名已更改的表：-

CREATE TABLE person
(
  id bigint NOT NULL,
  age smallint NOT NULL,
  "createdDate" timestamp without time zone NOT NULL,
  dateofbirth date NOT NULL,
  firstname character varying(255) NOT NULL,
  gender character varying(255) NOT NULL,
  lastname character varying(255) NOT NULL,
  lastupdateddate timestamp without time zone NOT NULL,
  middlename character varying(255) NOT NULL,
  userid bigint,
  CONSTRAINT person_pkey PRIMARY KEY (id),
  CONSTRAINT fkd8ja1o2m8k25sf0mxvhu4c0ti FOREIGN KEY (userid)
  REFERENCES users (user_id) MATCH SIMPLE
  ON UPDATE NO ACTION ON DELETE NO ACTION
)
WITH (
  OIDS=FALSE
);
ALTER TABLE person
  OWNER TO root;

现在我重新启动服务器，出现了新的错误：-

Feb 21, 2017 11:26:07 AM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 1572 ms
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/D:/sts-bundle/pivotal-tc-server- developer-3.2.2.RELEASE/base-instance/wtpwebapps/FeePaymentPortal/WEB-INF/lib/slf4j-log4j12-1.6.6.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/D:/sts-bundle/pivotal-tc-server-developer-3.2.2.RELEASE/base-instance/wtpwebapps/FeePaymentPortal/WEB-INF/lib/slf4j-simple-1.7.7.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
INFO : org.springframework.web.context.ContextLoader - Root WebApplicationContext: initialization started
INFO : org.springframework.web.context.support.XmlWebApplicationContext - Refreshing Root WebApplicationContext: startup date [Tue Feb 21 11:26:11 IST 2017]; root of context hierarchy
INFO : org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loading XML bean definitions from ServletContext resource [/WEB-INF/spring/root-context.xml]
INFO : org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loading XML bean definitions from ServletContext resource [/WEB-INF/spring/security-context.xml]
INFO : org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor - JSR-330 'javax.inject.Inject' annotation found and supported for autowiring
WARN : org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl - HHH000402: Using Hibernate built-in connection pool (not for production use!)
ERROR: org.hibernate.tool.hbm2ddl.SchemaExport - HHH000389: Unsuccessful: alter table role drop constraint FKgg3583634e0ydkacyk8wbbm19
ERROR: org.hibernate.tool.hbm2ddl.SchemaExport - ERROR: relation "role" does not exist
ERROR: org.hibernate.tool.hbm2ddl.SchemaExport - HHH000389: Unsuccessful: alter table user_roles drop constraint FKhfh9dx7w3ubf1co1vdev94g3f
ERROR: org.hibernate.tool.hbm2ddl.SchemaExport - ERROR: relation "user_roles" does not exist
INFO : org.springframework.web.context.ContextLoader - Root WebApplicationContext: initialization completed in 7665 ms
INFO : org.springframework.web.servlet.DispatcherServlet - FrameworkServlet 'appServlet': initialization started
INFO : org.springframework.web.context.support.XmlWebApplicationContext -  Refreshing WebApplicationContext for namespace 'appServlet-servlet': startup date [Tue Feb 21 11:26:18 IST 2017]; parent: Root WebApplicationContext
INFO : org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loading XML bean definitions from ServletContext resource [/WEB-INF/spring/appServlet/servlet-context.xml]
INFO : org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor - JSR-330 'javax.inject.Inject' annotation found and supported for autowiring
INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping - Mapped "{[/],methods=[GET]}" onto public java.lang.String org.giks.controllers.HomeController.home(org.springframework.ui.ModelMap)
INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping - Mapped "{[/payment-month],methods=[GET]}" onto public java.lang.String org.giks.controllers.HomeController.paymentMonth(org.springframework.ui.ModelMap)
INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping - Mapped "{[/payment-type],methods=[GET]}" onto public java.lang.String org.giks.controllers.HomeController.paymentMethod(org.springframework.ui.ModelMap)
INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping - Mapped "{[/payment-verified],methods=[GET]}" onto public java.lang.String org.giks.controllers.HomeController.paymentVerified(org.springframework.ui.ModelMap)
INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping - Mapped "{[/student-fees],methods=[GET]}" onto public java.lang.String org.giks.controllers.HomeController.getStudentFees(org.springframework.ui.ModelMap)
INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping - Mapped "{[/student-details],methods=[GET]}" onto public java.lang.String org.giks.controllers.HomeController.getStudentDetails(org.springframework.ui.ModelMap)
INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter - Looking for @ControllerAdvice: WebApplicationContext for namespace 'appServlet-servlet': startup date [Tue Feb 21 11:26:18 IST 2017]; parent:  Root WebApplicationContext
INFO : org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter - Looking for @ControllerAdvice: WebApplicationContext for namespace 'appServlet-servlet': startup date [Tue Feb 21 11:26:18 IST 2017]; parent: Root WebApplicationContext
INFO : org.springframework.web.servlet.handler.SimpleUrlHandlerMapping - Mapped URL path [/resources/**] onto handler 'org.springframework.web.servlet.resource.ResourceHttpRequestHandler#0'
INFO : org.springframework.web.servlet.DispatcherServlet - FrameworkServlet 'appServlet': initialization completed in 2426 ms
Feb 21, 2017 11:26:21 AM org.apache.catalina.startup.Catalina start
INFO: Server startup in 14090 ms

Answer 1

我认为主要的问题是PostgreSQL列名不区分大小写（默认情况下，它会将不带引号的列名转换为小写），但Hibernate是

例如，对于原始的createddate列：

• 您的域类指定createdDate，大写D
• 您的表使用createddate，小写D
• Hibernate在尝试更新架构（Hibernate.hbm2ddl.auto=update）时，会查找域类中指定的名为createdDate的列，但找不到，因为"createddate" != "createdDate"区分大小写，因此认为需要添加该列，并尝试这样做
• 根据PostgreSQL（不区分大小写），添加操作失败，因为存在具有等效名称的列

所以你的选择是：

1. 在域类中指定小写列名，或
2. 确保表中的列名使用匹配的大小写，注意在列创建语句中使用you must quote the column name以使其保留大小写

如您所见，当您手动将表列名更改为createdDate时，它解决了第一个错误（从而公开了一个新错误）

至于你关于“关系……不存在”的新错误，我不完全确定，但我认为this is also connected to case-sensitivity issues in table names，你必须进一步调查。至少，这是一种可能性

我没有在Hibernate中充分使用PostgreSQL来知道是否有更简单的选项，例如，一些方言选项或某个地方可以让它们一起玩得更好