Hibernate:在MySQL中,constraintName为null

Question

我有一个使用JPA和Hibernate 3.3.x的代码.此Java代码可以与存储在Oracle 10g或MySQL 5.1.x上的模式一起使用.使用约束定义表以定义唯一记录.发生约束冲突时,我想从异常中检索约束名称.

使用Oracle,可以正确检索约束名称.使用MySQL,约束名称为NULL.

知道如何用MySQL获取约束名称吗？

谢谢

说过

Answer 1

我想出了以下解决方案:

1. 扩展现有的Hibernate MySQL5Dialect:

   public class MySQL5Dialect extends org.hibernate.dialect.MySQL5Dialect {
   
       /**
       * Pattern to extract violated constraint name from {@link SQLException}.
       */
       private static final Pattern PATTERN = Pattern.compile(".*constraint\\W+(\\w+).*", Pattern.CASE_INSENSITIVE);
   
       private ViolatedConstraintNameExtracter constraintNameExtracter;
   
       public MySQL5Dialect() {
           constraintNameExtracter = new ConstraintNameExtractor();
       }
   
       @Override
       public ViolatedConstraintNameExtracter getViolatedConstraintNameExtracter() {
           return constraintNameExtracter;
       }
   
       private class ConstraintNameExtractor implements ViolatedConstraintNameExtracter {
   
           @Override
           public String extractConstraintName(SQLException sqle) {
               final String msg = sqle.getMessage();
               final Matcher matcher = PATTERN.matcher(msg);
               String constraintName = null;
               if (matcher.matches()) {
                   constraintName = matcher.group(1);
               }
   
               return constraintName;
           }
   
       }
   
   }
   

2. 在Hibernate配置文件(hibernate.cfg.xml)中指定新创建的方言:

   <property name="dialect">your.package.MySQL5Dialect</property>
   

3. 现在getConstraintName()将返回实际违反的约束名称:

   try {
       ...
   } catch (ConstraintViolationException e) {
       LOG.error(String.format("Constraint=%s, code=%d", e.getConstraintName(), e.getErrorCode()));
   }