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java.lang.ClassNotFoundException: Cannot find class: DB_VENDOR
在mybatis 中使用databaseIdProvider节点配置项(<databaseIdProvider type="DB_VENDOR">)时, 出现如下错误提示:
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_VENDOR at 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_VENDOR at 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 more Caused 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_VENDOR at 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 more Caused by: org.apache.ibatis.type.TypeException: Could not resolve type alias 'DB_VENDOR'. Cause: java.lang.ClassNotFoundException: Cannot find class: DB_VENDOR at 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 more Caused by: java.lang.ClassNotFoundException: Cannot find class: DB_VENDOR at 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是从3.2.3版本开始使用的别名,3.2.3(不含)以前的板本不支持此名称,需要使用VENDOR。
从mybatis源代码中可以看出:
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文件初始化时,使用了VENDOR转换,可以同时支持老板本的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以前的代码中,则不支持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); } } }
因此如果在使用旧的包,而又对应使用新的文档开发时,很可能引发此问题
java.lang.ClassNotFoundException: Cannot find class: DB_VENDOR
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