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出现问题：

Exception in thread "main" java.lang.AbstractMethodError: Method com/mchange/v2/c3p0/impl/NewProxyResultSet.getNString(Ljava/lang/String;)Ljava/lang/String; is abstract
    at com.mchange.v2.c3p0.impl.NewProxyResultSet.getNString(NewProxyResultSet.java)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.ibatis.logging.jdbc.ResultSetLogger.invoke(ResultSetLogger.java:68)
    at com.sun.proxy.$Proxy24.getNString(Unknown Source)
    at org.apache.ibatis.type.NStringTypeHandler.getNullableResult(NStringTypeHandler.java:37)
    at org.apache.ibatis.type.NStringTypeHandler.getNullableResult(NStringTypeHandler.java:26)
    at org.apache.ibatis.type.BaseTypeHandler.getResult(BaseTypeHandler.java:66)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.applyAutomaticMappings(DefaultResultSetHandler.java:498)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:385)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:339)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:314)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:287)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:183)
    at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64)
    at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
    at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)
    at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325)
    at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
    at com.sun.proxy.$Proxy21.selectOne(Unknown Source)
    at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:166)
    at ssm.dao.UserDaoImpl.findUserById(UserDaoImpl.java:13)
    at daoTest.main(daoTest.java:18)

解决方法：


更改C3p0版本

我的是把0.9.2.1 换成0.9.5.2，maven配置如下。

<dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.2.1</version>
 </dependency>

换成

<dependency>
    <groupId>com.mchange</groupId>
    <artifactId>c3p0</artifactId>
    <version>0.9.5.2</version>
</dependency>

如果不是Maven共工程，找相同jar包即可