java.lang.ClassNotFoundException: Cannot find class: DB_VENDOR

標籤：cannot find class   db_vendor   mybatis   

在mybatis 中使用databaseIdProvider節點配置項（<databaseIdProvider type="DB_VENDOR">）時， 出現如下錯誤提示：

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: ### Error building SqlSession.### The error may exist in SQL Mapper Configuration### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'DB_VENDOR'.  Cause: java.lang.ClassNotFoundException: Cannot find class: DB_VENDORat org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:23)at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:79)at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:63)at testMybatis.Test.main(Test.java:20)Caused by: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'DB_VENDOR'.  Cause: java.lang.ClassNotFoundException: Cannot find class: DB_VENDORat org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:106)at org.apache.ibatis.builder.xml.XMLConfigBuilder.parse(XMLConfigBuilder.java:89)at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:77)... 2 moreCaused by: org.apache.ibatis.builder.BuilderException: Error resolving class. Cause: org.apache.ibatis.type.TypeException: Could not resolve type alias 'DB_VENDOR'.  Cause: java.lang.ClassNotFoundException: Cannot find class: DB_VENDORat org.apache.ibatis.builder.BaseBuilder.resolveClass(BaseBuilder.java:100)at org.apache.ibatis.builder.xml.XMLConfigBuilder.databaseIdProviderElement(XMLConfigBuilder.java:244)at org.apache.ibatis.builder.xml.XMLConfigBuilder.parseConfiguration(XMLConfigBuilder.java:102)... 4 moreCaused by: org.apache.ibatis.type.TypeException: Could not resolve type alias 'DB_VENDOR'.  Cause: java.lang.ClassNotFoundException: Cannot find class: DB_VENDORat org.apache.ibatis.type.TypeAliasRegistry.resolveAlias(TypeAliasRegistry.java:114)at org.apache.ibatis.builder.BaseBuilder.resolveAlias(BaseBuilder.java:127)at org.apache.ibatis.builder.BaseBuilder.resolveClass(BaseBuilder.java:98)... 6 moreCaused by: java.lang.ClassNotFoundException: Cannot find class: DB_VENDORat org.apache.ibatis.io.ClassLoaderWrapper.classForName(ClassLoaderWrapper.java:188)at org.apache.ibatis.io.ClassLoaderWrapper.classForName(ClassLoaderWrapper.java:87)at org.apache.ibatis.io.Resources.classForName(Resources.java:254)at org.apache.ibatis.type.TypeAliasRegistry.resolveAlias(TypeAliasRegistry.java:110)... 8 more

原因是DB_VENDOR是從3.2.3版本開始使用的別名，3.2.3(不含)以前的板本不支援此名稱，需要使用VENDOR。

從mybatis原始碼中可以看出：

V3.2.3

package org.apache.ibatis.session;public class Configuration {  public Configuration() {    typeAliasRegistry.registerAlias("JDBC", JdbcTransactionFactory.class);    typeAliasRegistry.registerAlias("MANAGED", ManagedTransactionFactory.class);    typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);    typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);    typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);    typeAliasRegistry.registerAlias("PERPETUAL", PerpetualCache.class);    typeAliasRegistry.registerAlias("FIFO", FifoCache.class);    typeAliasRegistry.registerAlias("LRU", LruCache.class);    typeAliasRegistry.registerAlias("SOFT", SoftCache.class);    typeAliasRegistry.registerAlias("WEAK", WeakCache.class);    typeAliasRegistry.registerAlias("DB_VENDOR", VendorDatabaseIdProvider.class);    typeAliasRegistry.registerAlias("XML", XMLLanguageDriver.class);    typeAliasRegistry.registerAlias("RAW", RawLanguageDriver.class);    typeAliasRegistry.registerAlias("SLF4J", Slf4jImpl.class);    typeAliasRegistry.registerAlias("COMMONS_LOGGING", JakartaCommonsLoggingImpl.class);    typeAliasRegistry.registerAlias("LOG4J", Log4jImpl.class);    typeAliasRegistry.registerAlias("LOG4J2", Log4j2Impl.class);    typeAliasRegistry.registerAlias("JDK_LOGGING", Jdk14LoggingImpl.class);    typeAliasRegistry.registerAlias("STDOUT_LOGGING", StdOutImpl.class);    typeAliasRegistry.registerAlias("NO_LOGGING", NoLoggingImpl.class);    typeAliasRegistry.registerAlias("CGLIB", CglibProxyFactory.class);    typeAliasRegistry.registerAlias("JAVASSIST", JavassistProxyFactory.class);    languageRegistry.setDefaultDriverClass(XMLLanguageDriver.class);    languageRegistry.register(RawLanguageDriver.class);  }}

而在3.2.3的xml檔案初始化時，使用了VENDOR轉換，可以同時支援老闆本的VENDOR：

package org.apache.ibatis.builder.xml;public class XMLConfigBuilder extends BaseBuilder {  private void databaseIdProviderElement(XNode context) throws Exception {    DatabaseIdProvider databaseIdProvider = null;    if (context != null) {      String type = context.getStringAttribute("type");      if ("VENDOR".equals(type)) type = "DB_VENDOR";// awful patch to keep backward compatibility      Properties properties = context.getChildrenAsProperties();      databaseIdProvider = (DatabaseIdProvider) resolveClass(type).newInstance();      databaseIdProvider.setProperties(properties);    }  }}

 

而在3.2.3以前的代碼中，則不支援DB_VENDOR：

V3.2.2

package org.apache.ibatis.session;public class Configuration {  public Configuration() {    typeAliasRegistry.registerAlias("JDBC", JdbcTransactionFactory.class);    typeAliasRegistry.registerAlias("MANAGED", ManagedTransactionFactory.class);    typeAliasRegistry.registerAlias("JNDI", JndiDataSourceFactory.class);    typeAliasRegistry.registerAlias("POOLED", PooledDataSourceFactory.class);    typeAliasRegistry.registerAlias("UNPOOLED", UnpooledDataSourceFactory.class);    typeAliasRegistry.registerAlias("PERPETUAL", PerpetualCache.class);    typeAliasRegistry.registerAlias("FIFO", FifoCache.class);    typeAliasRegistry.registerAlias("LRU", LruCache.class);    typeAliasRegistry.registerAlias("SOFT", SoftCache.class);    typeAliasRegistry.registerAlias("WEAK", WeakCache.class    typeAliasRegistry.registerAlias("VENDOR", VendorDatabaseIdProvider.class);    typeAliasRegistry.registerAlias("XML", XMLLanguageDriver.class);    typeAliasRegistry.registerAlias("RAW", RawLanguageDriver.class);    typeAliasRegistry.registerAlias("SLF4J", Slf4jImpl.class);    typeAliasRegistry.registerAlias("COMMONS_LOGGING", JakartaCommonsLoggingImpl.class);    typeAliasRegistry.registerAlias("LOG4J", Log4jImpl.class);    typeAliasRegistry.registerAlias("JDK_LOGGING", Jdk14LoggingImpl.class);    typeAliasRegistry.registerAlias("STDOUT_LOGGING", StdOutImpl.class);    typeAliasRegistry.registerAlias("NO_LOGGING", NoLoggingImpl.class);        typeAliasRegistry.registerAlias("CGLIB", CglibProxyFactory.class);    typeAliasRegistry.registerAlias("JAVASSIST", JavassistProxyFactory.class);        languageRegistry.setDefaultDriverClass(XMLLanguageDriver.class);    languageRegistry.register(RawLanguageDriver.class);  }}

 

package org.apache.ibatis.builder.xml;public class XMLConfigBuilder extends BaseBuilder {    private void databaseIdProviderElement(XNode context) throws Exception {    DatabaseIdProvider databaseIdProvider = null;    if (context != null) {      String type = context.getStringAttribute("type");      Properties properties = context.getChildrenAsProperties();      databaseIdProvider = (DatabaseIdProvider) resolveClass(type).newInstance();      databaseIdProvider.setProperties(properties);    }    Environment environment = configuration.getEnvironment();    if (environment != null && databaseIdProvider != null) {      String databaseId = databaseIdProvider.getDatabaseId(environment.getDataSource());      configuration.setDatabaseId(databaseId);    }  }}

因此如果在使用舊的包，而又對應使用新的文檔開發時，很可能引發此問題

java.lang.ClassNotFoundException: Cannot find class: DB_VENDOR