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。