oracle blob和 varchar2互相转换，mybatis 读取blob乱码等相关问题总结

utl_raw.cast_to_raw

Oracle字符集查询

NLS_CHARACTERSET是数据库字符集，NLS_NCHAR_CHARACTERSET是国家字符集
ORACLE中有两大类字符型数据，VARCHAR2是按照数据库字符集来存储数据。而NVARCHAR2是按照国家字符集存储数据的。同样，CHAR和NCHAR也一样，一是数据库字符符，一是国家字符集。
字符集不同，二进制码的组合就不同

需求要求varchar2 加工插入blob

采用 utl_raw.cast_to_raw（‘你好啊’）,

mybatis 读取byte[] 转string

package com.hcp.util;


import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;

import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.sql.*;

public class BlobToStringTypeHandler extends BaseTypeHandler<String> {
    private static final String DEFAULT_CHARSET = "gbk";
    // 这里和数据库编码一直，否则乱码、 实体保存的时候也要 getBytes("gbk")

    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, String parameter, JdbcType jdbcType) throws SQLException {
        ps.setString(i, parameter);
    }

    @Override
    public String getNullableResult(ResultSet rs, String columnName) throws SQLException {
        Blob blob = rs.getBlob(columnName);
        return handle(blob);
    }

    @Override
    public String getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        Blob blob = rs.getBlob(columnIndex);
        return handle(blob);
    }

    @Override
    public String getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        Blob blob = cs.getBlob(columnIndex);
        return handle(blob);
    }

    private String handle( Blob blob)throws SQLException{
        try {
            return blob == null?null:new String(blob.getBytes(1, (int)blob.length()),DEFAULT_CHARSET);
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return  null;
    }
}

<resultMap  id="ResultMapWithHcpPjyjCx" type="HcpPjyjCx">
		<id column="PJYJXH" jdbcType="VARCHAR" property="pjyjxh" />
		<result column="PJJGXH" jdbcType="VARCHAR" property="pjjgxh" />
		<result column="PJLY_DM" jdbcType="VARCHAR" property="pjlyDm" />
		<result column="PJLYMC" jdbcType="VARCHAR" property="pjlyMc" />
		<result column="YJJY" jdbcType="BLOB" property="yjjy" />
		<result property="yjjynr" column="YJJYNR" jdbcType="BLOB"  typeHandler="com.hcp.util.BlobToStringTypeHandler"></result>
	</resultMap>