基于Oracle的数据缓存实现

1,在Oracle上建立一个Java source程序,用于更新本地文件:
create or replace and compile java source named javaupdatefile as
import java.io.*;

public class UpdFile
{
  public static void updateFile(String filename)
  {
 try{
    File f = new File(filename);
    f.delete();
    f.createNewFile();
 }catch{IOException e){
           //log exception
        }
  }
};

2,建立一个PL/SQL包,用于调用Java程序:
create or replace package cacheTest
as

procedure upd_File(p_filename varchar2)
is language Java name 'UpdFile.updateFile(java.lang.String)';

end catcheTest;

3,在表上建立触发器(表名为test):
create or replace trigger cacheTest
after update on test
for each row
declare
begin
 cacheTest.upd_File('d:\\Cache_testing.txt');
end cacheTest;

4,给数据库用户赋于执行更新文件的权限(这里的数据库连接用户为TEST):
execute dbms_java.grant_permission('TEST','SYS:java.io.FilePermission','d:\Cache_testing.txt','delete');
execute dbms_java.grant_permission('TEST','SYS:java.io.FilePermission','d:\Cache_testing.txt','write');