hibernate重复映射

错误显示： net.sf.hibernate.PropertyValueException: not-null property references a null or transient value: com.Order.customer
部分原文件：（ customer 和 order 类关系：一对多关联）
Order.hbm.xml
……………
< many-to-one
        name = "customer"
        column = "CUSTOMER_ID"
        class = "com.Customer"
        not-null = "true"
        cascade = "save-update"
    
     />
执行文件：
………
Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      // Create some data and persist it
     tx = session.beginTransaction();

     Customer customer=new Customer();
     customer.setName("Jack");
   
     Order order=new Order();
     order.setOrderNumber("Jack_Order001");
         session.save(customer);
         session.save(order);
   tx.commit();
原因分析：因为在执行代码中，没有将 customer 和 order 类一对多关联起来，若单独持久化两个类： session.save(customer);session.save(order); 则在保存 order 的时候，由于 CUSTOMER_ID是与 customer类外键，因此无法读取 customer_id, 而在 order.hbm.xml 中指定其不为空，则产生了以上错误。
问题解决： not-null = "true" 改为：not-null="false" 虽然程序无问题，但order表 CUSTOMER_ID为空，不符合逻辑。应该将指定其一对多的关联。
order.setCustomer(customer);
      customer.getOrders().add(order);

2〉
错误显示： RROR SessionImpl:2400 - Could not synchronize database state with session
net.sf.hibernate.exception.GenericJDBCException: could not delete collection: [com.Customer.orders#2]
部分原文件：
Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      tx = session.beginTransaction();
      Customer customer=(Customer)session.load(Customer.class,new Long(3));
      session.delete(customer);
      tx.commit();
原因分析：因为 cascade默认值为 none，所以当删除customer时，不会自动删除与其关联的order对象。
问题解决：添加语句 cascade = "delete"

3>
错误显示：
17:24:34,992 ERROR JDBCExceptionReporter:58 - [Microsoft][SQLServer 2000 Driver for JDBC][SQLServer]在关键字 'ORDER' 附近有语法错误。
17:24:34,992  WARN JDBCExceptionReporter:57 - SQL Error: 156, SQLState: HY000
17:24:35,002 ERROR JDBCExceptionReporter:58 - [Microsoft][SQLServer 2000 Driver for JDBC][SQLServer]在关键字 'ORDER' 附近有语法错误。
17:24:35,022  WARN JDBCExceptionReporter:34 - SQL Warning: 0, SQLState:
net.sf.hibernate.exception.GenericJDBCException : could not initialize collection: [com.Customer.orders#2]
部分原文件： order.hbm.xml
< hibernate-mapping >
  < class name = "com.Order" table = "ORDER" >
     < id name = "id" type = "long" column = "ID" >
        < generator class = "increment" />
      </ id >
   < property name = "orderNumber" type = "string" >
        < column name = "ORDER_NUMBER" length = "15" />
      </ property >
    
      < many-to-one
        name = "customer"
        column = "CUSTOMER_ID"
        class = "com.Customer"
        outer-join = "true" 
       />
原因分析：因为 order 表在 SQL 2000 数据库中已经定义了，如果用户在定义了 order 表，并且程序对该表进行连接等操作就会出错
问题解决：将 引用 order 处改为 [order]
< class name = "com.Order" table = "[ORDER]" >

4>
net.sf.hibernate.exception.SQLGrammarException : Could not save object
    at net.sf.hibernate.exception.SQLStateConverter.convert( SQLStateConverter.java:58 )
    at net.sf.hibernate.exception.JDBCExceptionHelper.convert( JDBCExceptionHelper.java:29 )
    at net.sf.hibernate.impl.SessionImpl.convert( SessionImpl.java:4131 )
    at net.sf.hibernate.impl.SessionImpl.saveWithGeneratedIdentifier( SessionImpl.java:794 )
    at net.sf.hibernate.impl.SessionImpl.save( SessionImpl.java:749 )
    at com.BusinessService.saveCategoryWithCascade( BusinessService.java:54 )
    at com.BusinessService.test( BusinessService.java:104 )
    at com.BusinessService.main( BusinessService.java:109 )
Caused by: java.sql.SQLException : [Microsoft][SQLServer 2000 Driver for JDBC][SQLServer]对象名 'CATEGORIES' 无效。
5〉
错误显示： net.sf.hibernate.MappingException : Resource: Add valid path not found
部分原文件： hibernate.hbm.xml
< hibernate-configuration >

< session-factory >
    < property name = "connection.username" > sa </ property >
    < property name = "connection.url" > jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=test </ property >
    < property name = "dialect" > net.sf.hibernate.dialect.SQLServerDialect </ property >
    < property name = "myeclipse.connection.profile" > MSSQL </ property >
    < property name = "connection.password" > hheryh </ property >
    < property name = "connection.driver_class" > com.microsoft.jdbc.sqlserver.SQLServerDriver </ property >
    < mapping resource = "Add valid path" />
</ session-factory >
原因分析：找不到有效的 xml 文件
问题解决：将所有配置文件都加到 resource 里
将< mapping resource = "Add valid path" />改为
< mapping resource = "com/Customer.hbm.xml" />
< mapping resource = "com/Order.hbm.xml" />
6〉 错误显示
net.sf.hibernate.MappingException : Error reading resource: com/Customer.hbm.xml
    at net.sf.hibernate.cfg.Configuration.addResource( Configuration.java:340 )
    at net.sf.hibernate.cfg.Configuration.doConfigure( Configuration.java:1027 )
    at net.sf.hibernate.cfg.Configuration.doConfigure( Configuration.java:983 )
    at net.sf.hibernate.cfg.Configuration.configure( Configuration.java:911 )
    at net.sf.hibernate.cfg.Configuration.configure( Configuration.java:897 )
    at com.BusinessService.<clinit>( BusinessService.java:17 )
Caused by: net.sf.hibernate.MappingException : duplicate import: Customer
    at net.sf.hibernate.cfg.Mappings.addImport( Mappings.java:85 )
    at net.sf.hibernate.cfg.Binder.bindClass( Binder.java:126 )
    at net.sf.hibernate.cfg.Binder.bindRootClass( Binder.java:221 )
    at net.sf.hibernate.cfg.Binder.bindRoot( Binder.java:1256 )
    at net.sf.hibernate.cfg.Configuration.add( Configuration.java:253 )
    at net.sf.hibernate.cfg.Configuration.addInputStream( Configuration.java:289 )
    at net.sf.hibernate.cfg.Configuration.addResource( Configuration.java:337 )
    ... 5 more
部分原文件 :hibernate.hbm.xml
<? xml version = '1.0' encoding = 'UTF-8' ?>
<! DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 2.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd" >

<!-- Generated by MyEclipse Hibernate Tools.                   -->
< hibernate-configuration >

< session-factory >
    < property name = "connection.username" > sa </ property >
    < property name = "connection.url" > jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=test </ property >
    < property name = "dialect" > net.sf.hibernate.dialect.SQLServerDialect </ property >
    < property name = "myeclipse.connection.profile" > MSSQL </ property >
    < property name = "connection.password" > hheryh </ property >
    < property name = "connection.driver_class" > com.microsoft.jdbc.sqlserver.SQLServerDriver </ property >
    < mapping resource = "com/Customer.hbm.xml" />
</ session-factory >

</ hibernate-configuration >

主程序：
static{
     try{
      // Create a configuration based on the properties file we've put
       Configuration config = new Configuration();
       config.addClass(Customer.class);
      // Get the session factory we can use for persistence
      sessionFactory = config
      .configure()
      .buildSessionFactory();
    }catch(Exception e){e.printStackTrace();}

  }
解决方法： config.addClass(Customer.class);
sessionFactory = config.configure().buildSessionFactory();

原因分析： hibernaet 配置文件有两种格式，一种是 xml 格式，一种是普通的 .property 格式 .
在 1.2 版本中，编译时自动会在 path 路径中查找 property 格式的配置文件。但不会查询 xml 格式的配置文件，因此需要在程序中手动添加 config.configure() ，但此时就不要加载了。
上面的程序 加载了一次 config.configure() ，又映射了一次，所以出错。

解决方法：
若配置文件为 xml 格式的，程序编写如下：
// Create a configuration based on the properties file we've put
       Configuration config = new Configuration();
             // Get the session factory we can use for persistence
      sessionFactory = config
      .configure()
.buildSessionFactory();

若配置文件为 property 格式的，程序编写如下：
// Create a configuration based on the properties file we've put
       Configuration config = new Configuration();
       config.addClass(Customer.class);
      // Get the session factory we can use for persistence
      sessionFactory = config.buildSessionFactory();


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7、Duplicate class/entity mapping 报错的问题
Could not parse configuration: /hibernate.cfg
Caused by: org.hibernate.DuplicateMappingException: Duplicate class/entity mapping
Caused by: org.dom4j.DocumentException: FWK005 parse may not be called while pa
sing. Nested exception: FWK005 parse may not be called while parsing.

这些错误的解决方法：
总结：
HibernateSessionFactory 中 getSession() 方法加一个 synchronized
或者检查一下是否用了两个数据连接形式，保证使用的是单一实例