CLOB与BLOB的区别及用途

BLOB和CLOB都是大字段类型，BLOB是按二进制来存储的，而CLOB是可以直接存储文字的。

其实两个是可以互换的的，或者可以直接用LOB字段代替这两个。但是为了更好的管理
ORACLE数据库，
通常像图片、文件、音乐等信息就用BLOB字段来存储，先将文件转为二进制再存储进去。
而像文章或者是较长的文字，就用CLOB存储，这样对以后的查询更新
存储等操作都提供很大的方便。

CLOB 定义

数据库中的一种保存文件所使用的类型。

Character Large Object

SQL 类型 CLOB 在 JavaTM 编程语言中的映射关系。SQL CLOB 是内置类型，它将字符大对象 (Character Large Object) 存储为数据库表某一行中的一个列值。默认情况下，驱动程序使用 SQL locator(CLOB) 实现 Clob 对象，这意味着 CLOB 对象包含一个指向 SQL CLOB 数据的逻辑指针而不是数据本身。Clob 对象在它被创建的事务处理期间有效。

在一些数据库系统里，也使用Text 作为CLOB的别名，比如SQL Server

BLOB 定义

BLOB (binary large object)，二进制大对象，是一个可以存储二进制文件的容器。

在计算机中，BLOB常常是数据库中用来存储二进制文件的字段类型。

BLOB是一个大文件，典型的BLOB是一张图片或一个声音文件，由于它们的尺寸，必须使用特殊的方式来处理（例如：上传、下载或者存放到一个数据库）。

根据Eric Raymond的说法，处理BLOB的主要思想就是让文件处理器（如数据库管理器）不去理会文件是什么，而是关心如何去处理它。

但也有专家强调，这种处理大数据对象的方法是把双刃剑，它有可能引发一些问题，如存储的二进制文件过大，会使数据库的性能下降。在数据库中存放体积较大的多媒体对象就是应用程序处理BLOB的典型例子。

CLOB和BLOB的区别

CLOB使用CHAR来保存数据。如：保存XML文档。

   BLOB就是使用二进制保存数据。 如：保存位图。

JAVA里面对CLOB的操作

在绝大多数情况下，使用2种方法使用CLOB

1 相对比较小的，可以用String进行直接操作，把CLOB看成字符串类型即可

2 如果比较大，可以用 getAsciiStream 或者 getUnicodeStream 以及对应的 setAsciiStream 和 setUnicodeStream 即可

读取数据

ResultSet rs = stmt.executeQuery(“SELECT TOP 1 * FROM Test1”);

rs.next();

Reader reader = rs.getCharacterStream(2);

插入数据

PreparedStatement pstmt = con.prepareStatement(“INSERT INTO test1 (c1_id, c2_vcmax) VALUES (?, ?)”);

pstmt.setInt(1, 1);

pstmt.setString(2, htmlStr);

pstmt.executeUpdate();

更新数据

Statement stmt = con.createStatemet();

ResultSet rs = stmt.executeQuery(“SELECT * FROM test1”);

rs.next();

Clob clob = rs.getClob(2);

long pos = clob.position(“dog”, 1);

clob.setString(1, “cat”, len, 3);

rs.updateClob(2, clob);

rs.updateRow();

JAVA中如何使用oracle中Clob类型字段

原文（全）
https://blog.csdn.net/jungeCSND/article/details/112567383

最近在项目中做接口对接需要把报文保存到数据库，本来声明列为VARCHAR2类型保存，但是后来在测试的时候发现报文长度过长，orcal中VARCHAR2最大只能保存4000个字符，因此导致错误，后来转为用cloub来保存报文，但是cloub比String操作起来较为麻烦，因此做了一个小demo来整理一下自己实现的方法：

1、建个测试表用来保存，查询数据如下：

-- Create table
create table PRPSSTEST
(id             INTEGER not null,requestapp     VARCHAR2(20),requestappname VARCHAR2(20),requestdate    DATE,requestdata    CLOB,responsedate   DATE,responsecode   VARCHAR2(10),responsedata   CLOB,attr           VARCHAR2(200),consumetime    INTEGER
)
tablespace TBS_ZSSALEpctfree 10initrans 1maxtrans 255storage(initial 64Knext 1Mminextents 1maxextents unlimited);

1、根据cloub字段值查询SQL
例：根据请求报文中包含“111”来查询

select * from prpsstest A where dbms_lob.instr(A.REQUESTDATA,'111',1,1) > 0;

2、SSH框架中使用Clob类型字段
实体类如下：
package com.sinosoft.entity;


// Generated by Hibernate Tools 3.2.0.b9 (sinosoft version)import static javax.persistence.GenerationType.SEQUENCE;import java.sql.Clob;
import java.util.Date;import javax.persistence.*;/*** generated by Tools.Don't edit.*/
@Entity
@Table(name = "PRPSSTEST")
public class PrpsSTest implements java.io.Serializable {private static final long serialVersionUID = 1L;private long id;private String requestapp;private String requestappname;private Date requestdate;private Clob requestdata;private Date responsedate;private String responsecode;private Clob responsedata;private String attr;private int consumetime;@SequenceGenerator(name = "generator", allocationSize = 1, sequenceName = "SEQ_prpsstest")@Id@GeneratedValue(strategy = SEQUENCE, generator = "generator")@Column(name = "id")public long getId() {return id;}public void setId(long id) {this.id = id;}@Column(name = "REQUESTAPP")public String getRequestapp() {return requestapp;}public void setRequestapp(String requestapp) {this.requestapp = requestapp;}@Column(name = "REQUESTAPPNAME")public String getRequestappname() {return requestappname;}public void setRequestappname(String requestappname) {this.requestappname = requestappname;}@Column(name = "REQUESTDATE")public Date getRequestdate() {return requestdate;}public void setRequestdate(Date requestdate) {this.requestdate = requestdate;}@Column(name = "REQUESTDATA")public Clob getRequestdata() {return requestdata;}public void setRequestdata(Clob requestdata) {this.requestdata = requestdata;} @Column(name = "RESPONSEDATE")public Date getResponsedate() {return responsedate;}public void setResponsedate(Date responsedate) {this.responsedate = responsedate;}@Column(name = "RESPONSECODE")public String getResponsecode() {return responsecode;}public void setResponsecode(String responsecode) {this.responsecode = responsecode;}@Column(name = "RESPONSEDATA")public Clob getResponsedata() {return responsedata;}public void setResponsedata(Clob responsedata) {this.responsedata = responsedata;} @Column(name = "ATTR")public String getAttr() {return attr;}public void setAttr(String attr) {this.attr = attr;}@Column(name = "CONSUMETIME")public int getConsumetime() {return consumetime;}public void setConsumetime(int consumetime) {this.consumetime = consumetime;}}

1，java中给cloub字段赋值：
Hibernate.createClob(“111”)

2、HQL根据CLOUB类型查询条件语句，与sql语句大同小异

3、查询出来的CLOUB字段转为String

public static String ClobToString(Clob clob) {String clobStr = "";Reader is = null;try {is = clob.getCharacterStream();BufferedReader br = new BufferedReader(is);String s = null;s = br.readLine();StringBuffer sb = new StringBuffer();while (s != null) {sb.append(s);s = br.readLine();}clobStr = sb.toString();} catch (IOException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}return clobStr;}

3、SpingBoot JPA框架中使用Clob类型字段
实体类如下：这里为了简便直接使用String对应数据库中cloub字段

package com.sinosoft.entity;// Generated by Hibernate Tools 3.2.0.b9 (sinosoft version)import static javax.persistence.GenerationType.SEQUENCE;import java.sql.Clob;
import java.util.Date;import javax.persistence.*;/*** generated by Tools.Don't edit.*/
@Entity
@Table(name = "PRPSSTEST")
public class PrpsSTest implements java.io.Serializable {private static final long serialVersionUID = 1L;private long id;private String requestapp;private String requestappname;private Date requestdate;private String requestdata;private Date responsedate;private String responsecode;private String responsedata;private String attr;private int consumetime;@SequenceGenerator(name = "generator", allocationSize = 1, sequenceName = "SEQ_prpsstest")@Id@GeneratedValue(strategy = SEQUENCE, generator = "generator")@Column(name = "id")public long getId() {return id;}public void setId(long id) {this.id = id;}@Column(name = "REQUESTAPP")public String getRequestapp() {return requestapp;}public void setRequestapp(String requestapp) {this.requestapp = requestapp;}@Column(name = "REQUESTAPPNAME")public String getRequestappname() {return requestappname;}public void setRequestappname(String requestappname) {this.requestappname = requestappname;}@Column(name = "REQUESTDATE")public Date getRequestdate() {return requestdate;}public void setRequestdate(Date requestdate) {this.requestdate = requestdate;}@Lob@Basic(fetch = FetchType.EAGER)@Column(name="REQUESTDATA", columnDefinition="CLOB", nullable=true)public String getRequestdata() {return requestdata;}public void setRequestdata(String requestdata) {this.requestdata = requestdata;}@Column(name = "RESPONSEDATE")public Date getResponsedate() {return responsedate;}public void setResponsedate(Date responsedate) {this.responsedate = responsedate;}@Column(name = "RESPONSECODE")public String getResponsecode() {return responsecode;}public void setResponsecode(String responsecode) {this.responsecode = responsecode;}@Lob@Basic(fetch = FetchType.EAGER)@Column(name="RESPONSEDATA", columnDefinition="CLOB", nullable=true)public String getResponsedata() {return responsedata;}public void setResponsedata(String responsedata) {this.responsedata = responsedata;}@Column(name = "ATTR")public String getAttr() {return attr;}public void setAttr(String attr) {this.attr = attr;}@Column(name = "CONSUMETIME")public int getConsumetime() {return consumetime;}public void setConsumetime(int consumetime) {this.consumetime = consumetime;}}

1、使用JPA根据Cloub字段值查询语句：
@Query(value = "select * from PrpsSTest where dbms_lob.instr(requestdata,?1,1,1) > 0 ",nativeQuery = true)
public PrpsSTest getTestByRequestData(String usercode);