为了实现在用户误操作后能够对数据进行修正，打算添加一个数据库管理功能，主要实现对数据表的查询和执行sql语句。费了半天功夫完成以后查询有的表数据正常显示，但是个别表出现如下错误：
No Dialect mapping for JDBC type: -1
意思显而易见：没有方言能够与JDBC类型-1映射。难道我数据库字段用了特殊类型，而hibernate不支持？百度之后找到很多同样错误，有的分析发现对于长度过大的varchar（LONGVARCHAR ）映射时会报这个错误，检查数据库发现这些表中都是用了text类型，应该就是这个原因。修改方法一般有两种：一是修改字段类型，二是扩展自定义方言。采用第二种方法修改如下：
添加自定义方言类：
package com.sxpt.util;import java.sql.Types;import org.hibernate.Hibernate;import org.hibernate.dialect.MySQL5Dialect;public class KtMySQL5Dialect extends MySQL5Dialect{ public KtMySQL5Dialect(){ super(); this.registerHibernateType(Types.LONGVARCHAR, Hibernate.STRING.getName()); }} hibernate.xml也要修改为对应方言：
com.sxpt.util.KtMySQL5Dialect
下附java.sql.Types对应值，在出现错误时可根据值判断类型
public final static int BIT = -7;public final static int TINYINT = -6;public final static int SMALLINT = 5;public final static int INTEGER = 4;public final static int BIGINT = -5;public final static int FLOAT = 6;public final static int REAL = 7;public final static int DOUBLE = 8;public final static int NUMERIC = 2;public final static int DECIMAL = 3;public final static int CHAR = 1;public final static int VARCHAR = 12;public final static int LONGVARCHAR = -1;public final static int DATE = 91;public final static int TIME = 92;public final static int TIMESTAMP = 93;public final static int BINARY = -2;public final static int VARBINARY = -3;public final static int LONGVARBINARY = -4;public final static int NULL = 0;public final static int OTHER = 1111;public final static int JAVA_OBJECT = 2000;public final static int DISTINCT = 2001;public final static int STRUCT = 2002;public final static int ARRAY = 2003;public final static int BLOB = 2004;public final static int CLOB = 2005;public final static int REF = 2006;public final static int DATALINK = 70;public final static int BOOLEAN = 16;public final static int ROWID = -8;public static final int NCHAR = -15;public static final int NVARCHAR = -9;public static final int LONGNVARCHAR = -16;public static final int NCLOB = 2011;public static final int SQLXML = 2009;