深入浅析mybatis oracle BLOB类型字段保存与读取

前端技术 2023/09/07 Oracle

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。

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