如何用jsp实现oracle数据库中的文件下载？？__varchar2_query_str_lobloc_buffer_number_

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如何用jsp实现oracle数据库中的文件下载？？

来源: 互联网发布时间：2015-07-16

本文导语: 我用的是jdk＋tomcat＋oracle8i, 如何实现数据库中文件的下载？ | updateclob create or replace procedure updateclob( table_name in varchar2, field_id in varchar2, field_name in varchar2, v_id in number, v_pos in number, v_clob in ...

我用的是jdk＋tomcat＋oracle8i,
如何实现数据库中文件的下载？

updateclob
create or replace procedure updateclob(
table_name in varchar2,
field_id in varchar2,
field_name in varchar2,
v_id in number,
v_pos in number,
v_clob in varchar2)
is
lobloc clob;
c_clob varchar2(32767);
amt binary_integer;
pos binary_integer;
query_str varchar2(1000);
begin
pos:=v_pos*32766+1;
amt := length(v_clob);
c_clob:=v_clob;
query_str :='select '||field_name||' from '||table_name||' where '||field_id||'= :id for update ';
--initialize buffer with data to be inserted or updated
EXECUTE IMMEDIATE query_str INTO lobloc USING v_id;
--from pos position, write 32766 varchar2 into lobloc
dbms_lob.write(lobloc, amt, pos, c_clob);
commit;
exception
when others then
rollback;
end;
我在oracle中是这样用的，你可以参考一下。

create or replace procedure updateclob(
table_name in varchar2,
field_id in varchar2,
field_name in varchar2,
v_id in number,
v_pos in number,
v_clob in varchar2)
is
lobloc clob;
c_clob varchar2(32767);
amt binary_integer;
pos binary_integer;
query_str varchar2(1000);
begin
pos:=v_pos*32766+1;
amt := length(v_clob);
c_clob:=v_clob;
query_str :='select '||field_name||' from '||table_name||' where '||field_id||'= :id for update ';
--initialize buffer with data to be inserted or updated
EXECUTE IMMEDIATE query_str INTO lobloc USING v_id;
--from pos position, write 32766 varchar2 into lobloc
dbms_lob.write(lobloc, amt, pos, c_clob);
commit;
exception
when others then
rollback;
end;
l /用法说明：
在插入或修改以前，先把其它字段插入或修改，CLOB字段设置为空empty_clob()，
然后调用以上的过程插入大于2048到32766个字符。
如果需要插入大于32767个字符，编一个循环即可解决问题。
查询CLOB的PL/SQL函数：getclob
create or replace function getclob(
table_name in varchar2,
field_id in varchar2,
field_name in varchar2,
v_id in number,
v_pos in number) return varchar2
is
lobloc clob;
buffer varchar2(32767);
amount number := 2000;
offset number := 1;
query_str varchar2(1000);
begin
query_str :='select '||field_name||' from '||table_name||' where '||field_id||'= :id ';
--initialize buffer with data to be found
EXECUTE IMMEDIATE query_str INTO lobloc USING v_id;
offset:=offset+(v_pos-1)*2000;
--read 2000 varchar2 from the buffer
dbms_lob.read(lobloc,amount,offset,buffer);
return buffer;
exception
when no_data_found then
return buffer;
end;

int pictureId=param.getIntParameter(request,"picture_id",0);
    JdbcConnect myQuery=new JdbcConnect();
    ResultSet rs = myQuery.executeQuery("SELECT * FROM picture where picture_id="+pictureId);
       int length = 0;
       if (rs.next())

      {
      BLOB my_blob = (BLOB)rs.getObject("picture");
      length = (int)my_blob.length();
      out.print(length);
      byte [] byte_array  = my_blob.getBytes(1, length);
      response.setContentType("image/jpeg");
    ServletOutputStream sos = response.getOutputStream();

    for(int i=0;i