解决mybatis在oracle中null的问题

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使用mybatis时遇到Error setting null parameter异常，常用的解决方式是在sql中指定jdbcType，这样的写法感觉有点罗嗦，后来参考spring jdbc中的实现方式，改写了mybatis中的BaseTypeHandler类，经测试ok。

以下是修改的类文件，修改的地方为19 ~ 36行。

package org.apache.ibatis.type;

import java.sql.CallableStatement;
import java.sql.DatabaseMetaData;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;

public abstract class BaseTypeHandler implements TypeHandler {

   public void setParameter(PreparedStatement ps, int i, Object parameter,
           JdbcType jdbcType) throws SQLException {
       if (parameter == null) {
           if (jdbcType == null) {
               try {
                   boolean useSetObject = false;
                   int sqlType = Types.NULL;
                   try {
                       DatabaseMetaData dbmd = ps.getConnection()
                               .getMetaData();
                       String databaseProductName = dbmd
                               .getDatabaseProductName();
                       String jdbcDriverName = dbmd.getDriverName();
                       if (databaseProductName.startsWith("Informix")
                               || jdbcDriverName
                                       .startsWith("Microsoft SQL Server")) {
                           useSetObject = true;
                       } else if (databaseProductName.startsWith("Oracle")
                               || databaseProductName.startsWith("DB2")
                               || jdbcDriverName.startsWith("jConnect")
                               || jdbcDriverName.startsWith("SQLServer")
                               || jdbcDriverName.startsWith("Apache Derby")) {
                           sqlType = Types.VARCHAR;
                       }
                   } catch (Throwable ex) {
                       throw new TypeException(
                               "Could not check database or driver name", ex);
                   }
                   if (useSetObject) {
                       ps.setObject(i, null);
                   } else {
                       ps.setNull(i, sqlType);
                   }

               } catch (SQLException e) {
                   throw new TypeException(
                           "Error setting null parameter. Most JDBC drivers require that the JdbcType must be specified for all nullable parameters. Cause: "
                                   + e, e);
               }
           } else {
               ps.setNull(i, jdbcType.TYPE_CODE);
           }
       } else {
           setNonNullParameter(ps, i, parameter, jdbcType);
       }
   }

   public Object getResult(ResultSet rs, String columnName)
           throws SQLException {
       Object result = getNullableResult(rs, columnName);
       if (rs.wasNull()) {
           return null;
       } else {
           return result;
       }
   }

   public Object getResult(CallableStatement cs, int columnIndex)
           throws SQLException {
       Object result = getNullableResult(cs, columnIndex);
       if (cs.wasNull()) {
           return null;
       } else {
           return result;
       }
   }

   public abstract void setNonNullParameter(PreparedStatement ps, int i,
           Object parameter, JdbcType jdbcType) throws SQLException;

   public abstract Object getNullableResult(ResultSet rs, String columnName)
           throws SQLException;

public abstract Object getNullableResult(CallableStatement cs, int columnIndex) throws SQLException;

}