【Oracle】【35】BLOB字段和CLOB字段

前言：

BLOB用来存储大量二进制数据。如图片、音乐等，转为二进制数再存储

CLOB用来存储大量文本数据。如HTML页面等，varchar2最大是4000，预计会超过4000的用Clob

正文：

1，我用的是java + mybatis，直接用String处理就可以了。String最大能存4G

数据库：创建表

-- Create table
create table CLOB_TEST
(
  id      VARCHAR2(32) default sys_guid(),
  content CLOB
)

实体类：

package com.bf.test.entity;

public class ClobTest {
    private String id;

    private String content;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

}

查询语句：sql.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.bf.labor.dao.IClobDao">   
  <resultMap id="BaseResultMap" type="com.bf.test.entity.ClobTest" >
    <result column="ID" property="id" jdbcType="VARCHAR" />
    <result column="CONTENT" property="content" jdbcType="VARCHAR" />
  </resultMap>
  
  <select id="getList" resultMap="BaseResultMap">
    select * from CLOB_TEST
  </select>
  
  <insert id="insert" >
    insert into CLOB_TEST (CONTENT)
    values (#{content})
  </insert>
  
</mapper>

测试类：

package com.test;

import java.util.List;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.web.WebAppConfiguration;

import com.bf.labor.entity.ClobTest;
import com.bf.labor.service.ClobService;

@RunWith(SpringJUnit4ClassRunner.class)
@WebAppConfiguration("web")
@ContextConfiguration(locations = "file:G:/WIM/Source/webapp/WEB-INF/spring-core-config.xml")
public class ClobServiceTest {
    @Autowired private ClobService clobService;
    
    @Test
    public void test() {
        List<ClobTest> list = this.clobService.getList();
        System.out.println("test=" + list);
    }
    
    @Test
    public void test2() {
        String str = "";
        for (int i = 0; i < 5000; i++) {
            str = str + "a";
        }
        System.out.println("str=" + str);
        
        ClobTest newInfo = new ClobTest();
        newInfo.setContent(str);
        this.clobService.insert(newInfo);
    }
}

2，Clob字段转换成字符串。数据库数据迁移的时候要格外注意这一点，不做处理的话，Clob字段的值为空

方法1：dbms_lob.substr()

注意：dbms_lob.substr(content)，超过4000字符，会报错

参考博客：

Oracle中将Clob字段转换成字符串 - sqyNick - CSDN博客
https://blog.csdn.net/u010670151/article/details/52210333