今天同事问我是否用过oracle中的CLOB类型,说实话-没听过。
百度了解了下，CLOB是oracle中用于存储文字的大字段类型、当需要存入大数据量（大于4000）时，varchar2不够用，可以使用clob。
Oracle中SQL语句中的两个单引号之间的字符数不能大于4000的限制。'" + data + "' data在sql语句之间，当data的值大于4000个字节时就会报错。
ORACLE - 往有CLOB类型的表中插数据
1.其他字段照常插入，CLOB类型字段先插入"empty_clob()"值 ( )。
2.把自动提交设为false，否则，再次查找时就不能正确更新
2.然后使用带有“for update”的查询语句锁定更新行。
3.最后实例化输出流并对CLOB类型字段数据进行插入操作。
tips:
1.CLOB类型的空对象为empty_clob()；
2.如果在插入前没有将自动提交设为false会报 “fetch out of sequence”；
3.如果不加for update会报：“row containing the LOB value is not locked”；
关键代码：
StringBuffer sqlstr = new StringBuffer();
sqlstr.append("INSERT INTO notice t (t.notice_id,t.notice_type,t.notice_title," +
"t.notice_status,t.sender,t.eff_date,t.exp_date,t.creater,t.create_time," +
"t.notice_content) VALUES (");
sqlstr.append(+notice.getNoticeId() + ",");
sqlstr.append("'" + notice.getNoticeType() + "',");
sqlstr.append("'" + notice.getNoticeTitle() + "',");
sqlstr.append("'" + notice.getNoticeStatus() + "',");
sqlstr.append("'" + notice.getSender() + "',");
sqlstr.append("sysdate,");
sqlstr.append("to_date('" + theForm.getEndDate2() + " 23:59:59','yyyy-MM-dd HH24:mi:ss'),");
sqlstr.append("'" + notice.getCreater() + "',");
sqlstr.append("sysdate,");
sqlstr.append("empty_clob()");//插入空值
sqlstr.append(")");
String sql = sqlstr.toString();
Class.forName(driverClassName);
Connection con = DriverManager.getConnection(url, username, password);
con.setAutoCommit(false);//设置不自动提交
PreparedStatement pstmt = con.prepareStatement(sql);
String content = notice.getNoticeContent().replace('\'', '\"');
try {
pstmt.execute();
con.commit();//插入
pstmt = con.prepareStatement("select notice_content from notice where notice_id="+notice.getNoticeId()+" for update");//查找刚刚插入的那条记录 for update
ResultSet res = pstmt.executeQuery();
CLOB clob = null;
while(res.next()){
clob = (oracle.sql.CLOB)res.getClob(1);
clob.putString(1, content);//content为前台提交过来的公告内容，大数据量
}
pstmt = con.prepareStatement("update notice set notice_content = ? where notice_id=?");//修改notice_content字段的内容
pstmt.setClob(1, clob);
pstmt.setLong(2, notice.getNoticeId());
pstmt.executeUpdate();
con.commit();
if (nps != null && nps.size() > 0) {
noticePartnerDao.saveOrUpdateAll(nps);
}
} catch (Exception e) {
info.setCode("1");
info.setFlag(false);
info.setInfo("发布公告失败!");
System.out.println(e.getMessage());
System.out.println(e.getStackTrace());
FileLog.errorLog(e, "发布公告失败");
return info;
} finally {
if(pstmt!=null) {
pstmt.close();
}
if(con!=null) {
con.close();
}
}
ORACLE - 查询带CLOB类型的数据,并把CLOB数据转为String类型
关键代码：
StringBuffer sqlstr = new StringBuffer();
sqlstr.append("INSERT INTO notice t (t.notice_id,t.notice_type,t.notice_title," +
"t.notice_status,t.sender,t.eff_date,t.exp_date,t.creater,t.create_time," +
"t.notice_content) VALUES (");
sqlstr.append(+notice.getNoticeId() + ",");
sqlstr.append("'" + notice.getNoticeType() + "',");
sqlstr.append("'" + notice.getNoticeTitle() + "',");
sqlstr.append("'" + notice.getNoticeStatus() + "',");
sqlstr.append("'" + notice.getSender() + "',");
sqlstr.append("sysdate,");
sqlstr.append("to_date('" + theForm.getEndDate2() + " 23:59:59','yyyy-MM-dd HH24:mi:ss'),");
sqlstr.append("'" + notice.getCreater() + "',");
sqlstr.append("sysdate,");
sqlstr.append("empty_clob()");//插入空值
sqlstr.append(")");
String sql = sqlstr.toString();
Class.forName(driverClassName);
Connection con = DriverManager.getConnection(url, username, password);
con.setAutoCommit(false);//设置不自动提交
PreparedStatement pstmt = con.prepareStatement(sql);
String content = notice.getNoticeContent().replace('\'', '\"');
try {
pstmt.execute();
con.commit();//插入
pstmt = con.prepareStatement("select notice_content from notice where notice_id="+notice.getNoticeId()+" for update");//查找刚刚插入的那条记录 for update
ResultSet res = pstmt.executeQuery();
CLOB clob = null;
while(res.next()){
clob = (oracle.sql.CLOB)res.getClob(1);
clob.putString(1, content);//content为前台提交过来的公告内容，大数据量
}
pstmt = con.prepareStatement("update notice set notice_content = ? where notice_id=?");//修改notice_content字段的内容
pstmt.setClob(1, clob);
pstmt.setLong(2, notice.getNoticeId());
pstmt.executeUpdate();
con.commit();
if (nps != null && nps.size() > 0) {
noticePartnerDao.saveOrUpdateAll(nps);
}
} catch (Exception e) {
info.setCode("1");
info.setFlag(false);
info.setInfo("发布公告失败!");
System.out.println(e.getMessage());
System.out.println(e.getStackTrace());
FileLog.errorLog(e, "发布公告失败");
return info;
} finally {
if(pstmt!=null) {
pstmt.close();
}
if(con!=null) {
con.close();
}
}
关键代码：
//oracle.sql.Clob类型转换成String类型public String ClobToString(Clob clob) {
String reString = "";
Reader is = null;
try {
is = clob.getCharacterStream();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// 得到流
BufferedReader br = new BufferedReader(is);
String s = null;
try {
s = br.readLine();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
StringBuffer sb = new StringBuffer();
while (s != null) {
//执行循环将字符串全部取出付值给StringBuffer由StringBuffer转成STRING
sb.append(s);
try {
s = br.readLine();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
reString = sb.toString();
return reString;
}
String
notice_content=ClobToString(rs.getClob("str"));
关键代码：
StringBuffer sqlstr = new StringBuffer();
sqlstr.append("INSERT INTO notice t (t.notice_id,t.notice_type,t.notice_title," +
"t.notice_status,t.sender,t.eff_date,t.exp_date,t.creater,t.create_time," +
"t.notice_content) VALUES (");
sqlstr.append(+notice.getNoticeId() + ",");
sqlstr.append("'" + notice.getNoticeType() + "',");
sqlstr.append("'" + notice.getNoticeTitle() + "',");
sqlstr.append("'" + notice.getNoticeStatus() + "',");
sqlstr.append("'" + notice.getSender() + "',");
sqlstr.append("sysdate,");
sqlstr.append("to_date('" + theForm.getEndDate2() + " 23:59:59','yyyy-MM-dd HH24:mi:ss'),");
sqlstr.append("'" + notice.getCreater() + "',");
sqlstr.append("sysdate,");
sqlstr.append("empty_clob()");//插入空值
sqlstr.append(")");
String sql = sqlstr.toString();
Class.forName(driverClassName);
Connection con = DriverManager.getConnection(url, username, password);
con.setAutoCommit(false);//设置不自动提交
PreparedStatement pstmt = con.prepareStatement(sql);
String content = notice.getNoticeContent().replace('\'', '\"');
try {
pstmt.execute();
con.commit();//插入
pstmt = con.prepareStatement("select notice_content from notice where notice_id="+notice.getNoticeId()+" for update");//查找刚刚插入的那条记录 for update
ResultSet res = pstmt.executeQuery();
CLOB clob = null;
while(res.next()){
clob = (oracle.sql.CLOB)res.getClob(1);
clob.putString(1, content);//content为前台提交过来的公告内容，大数据量
}
pstmt = con.prepareStatement("update notice set notice_content = ? where notice_id=?");//修改notice_content字段的内容
pstmt.setClob(1, clob);
pstmt.setLong(2, notice.getNoticeId());
pstmt.executeUpdate();
con.commit();
if (nps != null && nps.size() > 0) {
noticePartnerDao.saveOrUpdateAll(nps);
}
} catch (Exception e) {
info.setCode("1");
info.setFlag(false);
info.setInfo("发布公告失败!");
System.out.println(e.getMessage());
System.out.println(e.getStackTrace());
FileLog.errorLog(e, "发布公告失败");
return info;
} finally {
if(pstmt!=null) {
pstmt.close();
}
if(con!=null) {
con.close();
}
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