深入浅析mybatis oracle BLOB类型字段保存与读取

一、BLOB字段

　　BLOB是指二进制大对象也就是英文Binary Large Object的所写，而CLOB是指大字符对象也就是英文Character Large Object的所写。其中BLOB是用来存储大量二进制数据的；CLOB用来存储大量文本数据。BLOB通常用来保存图片、文件等二进制类型的数据。

二、使用mybatis操作blob

　　1、表结构如下：

create table BLOB_FIELD
(
ID VARCHAR2(64 BYTE) not null,
TAB_NAME VARCHAR2(64 BYTE) not null,
TAB_PKID_VALUE VARCHAR2(64 BYTE) not null,
CLOB_COL_NAME VARCHAR2(64 BYTE) not null,
CLOB_COL_VALUE CLOB,
constraint PK_BLOB_FIELD primary key (ID)
);

　　2、实体代码如下：

package com.test.entity;
import java.sql.Clob;
/**
* 大字段
*/
public class BlobField {
private String tabName;// 表名
private String tabPkidValue;// 主键值
private String blobColName;// 列名
private byte[] blobColValue;// 列值 clob类型
public String getTabName() {
return tabName;
}
public void setTabName(String tabName) {
this.tabName = tabName;
}
public String getTabPkidValue() {
return tabPkidValue;
}
public void setTabPkidValue(String tabPkidValue) {
this.tabPkidValue = tabPkidValue;
}
public String getBlobColName() {
return blobColName;
}
public void setBlobColName(String blobColName) {
this.blobColName = blobColName;
}
public byte[] getBlobColValue() {
return blobColValue;
}
public void setBlobColValue(byte[] blobColValue) {
this.blobColValue = blobColValue;
}
}

　　3、mybatis sql代码如下：

<?xml version="." encoding="UTF-" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper .//EN" "http://mybatis.org/dtd/mybatis--mapper.dtd">
<mapper namespace="com.test.dao.BlobFieldDao">
<sql id="blobFieldColumns">
a.ID AS id,
a.TAB_NAME AS tabName,
a.TAB_PKID_VALUE AS tabPkidValue,
a.BLOB_COL_NAME AS blobColName,
a.BLOB_COL_VALUE AS blobColValue
</sql>
<sql id="blobFieldJoins">
</sql>
<select id="get" resultType="blobField">
SELECT
<include refid="blobFieldColumns" />
FROM BLOB_FIELD a
<include refid="blobFieldJoins" />
WHERE a.ID = #{id}
</select>
<select id="findList" resultType="blobField">
SELECT
<include refid="blobFieldColumns" />
FROM BLOB_FIELD a
<include refid="blobFieldJoins" />
</select>
<insert id="insert">
INSERT INTO BLOB_FIELD(
ID ,
TAB_NAME ,
TAB_PKID_VALUE ,
BLOB_COL_NAME ,
BLOB_COL_VALUE
) VALUES (
#{id},
#{tabName},
#{tabPkidValue},
#{blobColName},
#{blobColValue,jdbcType=BLOB}
)
</insert>
<update id="update">
UPDATE BLOB_FIELD SET
TAB_NAME = #{tabName},
TAB_PKID_VALUE = #{tabPkidValue},
BLOB_COL_NAME = #{blobColName},
BLOB_COL_VALUE = #{blobColValue}
WHERE ID = #{id}
</update>
<delete id="delete">
DELETE FROM BLOB_FIELD
WHERE ID = #{id}
</delete>
</mapper>

　　3、controller代码如下：

　　a、保存BLOB字段代码

/**
* 附件上传
*
* @param testId
* 主表Id
* @param request
* @return
* @throws UnsupportedEncodingException
*/
@RequiresPermissions("exc:exceptioninfo:feedback")
@RequestMapping(value = "attachment", method = RequestMethod.POST)
@ResponseBody
public Map<String, Object> uploadAttachment(@RequestParam(value = "testId", required = true) String testId,

HttpServletRequest request)
throws UnsupportedEncodingException {
Map<String, Object> result = new HashMap<String, Object>();

MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
// 获得文件
MultipartFile multipartFile = multipartRequest.getFile("Filedata");// 与前端设置的fileDataName属性值一致
String filename = multipartFile.getOriginalFilename();// 文件名称
InputStream is = null;
try {
//读取文件流
is = multipartFile.getInputStream();
byte[] bytes = FileCopyUtils.copyToByteArray(is);
BlobField blobField = new BlobField();
blobField.setTabName("testL");
blobField.setTabPkidValue(testId);
blobField.setBlobColName("attachment");
blobField.setBlobColValue(bytes);
//保存blob字段
this.testService.save(blobField, testId, filename);
result.put("flag", true);
result.put("attachmentId", blobField.getId());
result.put("attachmentName", filename);
} catch (IOException e) {
e.printStackTrace();
result.put("flag", false);
} finally {
IOUtils.closeQuietly(is);
}
return result;
}

　　b、读取BLOB字段

/**
* 下载附件
*
* @param attachmentId
* @return
*/
@RequiresPermissions("exc:exceptioninfo:view")
@RequestMapping(value = "download", method = RequestMethod.GET)
public void download(@RequestParam(value = "attachmentId", required = true) String attachmentId,
@RequestParam(value = "attachmentName", required = true) String attachmentName, HttpServletRequest
request, HttpServletResponse response) {
ServletOutputStream out = null;
try {
response.reset();
String userAgent = request.getHeader("User-Agent");
byte[] bytes = userAgent.contains("MSIE") ? attachmentName.getBytes() : attachmentName.getBytes("UTF-
"); // fileName.getBytes("UTF-")处理safari的乱码问题
String fileName = new String(bytes, "ISO--");
// 设置输出的格式
response.setContentType("multipart/form-data");
response.setHeader("Content-Disposition", "attachment;fileName=" + URLEncoder.encode(attachmentName,
"UTF-"));
BlobField blobField = this.blobFieldService.get(attachmentId);
//获取blob字段
byte[] contents = blobField.getBlobColValue();
out = response.getOutputStream();
//写到输出流
out.write(contents);
out.flush();
} catch (IOException e) {
e.printStackTrace();
}
}

　　本例子将文件上传并保存到BLOB类型字段字段，下载的时候读取BLOB字段，并写入成输出流。

以上就是本文的全部叙述，希望对大家有所帮助。