java web和servlet结合使用为数据库备份

使用Runtime类的方法备份数据库和web下载结合起来，就可以得到想要的功能．源代码如下（tomcat+mysql)：  
 
   
 
 
 
package org.liuxuan.jsp;  
 
import java.io.*;  
import java.text.SimpleDateFormat;  
import javax.servlet.*;  
import javax.servlet.http.*;  
 
 
public class Backup extends HttpServlet ...{  
      
 
    public void doGet(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException ...{  
        SimpleDateFormat dateFm = new SimpleDateFormat("yyyy-MM-dd"); // 格式化当前系统日期  
        String dateTime = dateFm.format(new java.util.Date());  
        File file = null;  
        InputStream is = null;  
        String fileName = null;  
        int fileSize = 0;  
        String mysql = "mysqldump -uroot -p123456 rudisc > c:\" + dateTime+ ".sql";//mysql备份语句  
        try ...{  
            Process p=java.lang.Runtime.getRuntime().exec("cmd /c " + mysql);  
             while(true)...{         
                                                               if(p.waitFor()==0)       break;   //直到进程结束，才退出循环  
                                          }             
 
        } catch (Exception e) ...{  
            e.printStackTrace();  
        }  
 
        file = new File("c:\"+dateTime+".sql");  
        is = new FileInputStream(file);  
        fileName = file.getName();  
        fileSize = (int) file.length();  
 
        fileName = toUTF8String(fileName);  
        // 设置下载文件使用的报头域。  
        response.setContentType("application/x-msdownload");  
        String str = "attachment; filename=" + fileName;  
        response.setHeader("Content-Disposition", str);  
        response.setContentLength(fileSize);  
 
        // 得到响应对象的输出流，用于向客户端输出二进制数据。  
        ServletOutputStream sos = response.getOutputStream();  
        byte[] data = new byte[2048];  
        int len = 0;  
        while ((len = is.read(data)) > 0) ...{  
            sos.write(data, 0, len); // 向浏览器输出文件数据  
        }  
        is.close(); // 关闭输入流  
        sos.close();// 关闭输出流  
 
    }  
 
    public void doPost(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException ...{  
        doGet(request, response);  
    }  
                        
    public static String toUTF8String(String str) ...{  
        StringBuffer sb = new StringBuffer();  
        int len = str.length();  
 
        for (int i = 0; i < len; i++) ...{  
            char c = str.charAt(i);  
            if (c >= 0 && c <= 255) ...{  
                sb.append(c);  
            } else ...{  
                byte[] b;  
                try ...{  
                    b = Character.toString(c).getBytes("UTF-8");  
                } catch (UnsupportedEncodingException ex) ...{  
                    System.err.println(ex);  
                    b = null;  
                }  
                for (int j = 0; j < b.length; j++) ...{  
                    int k = b[j];  
                    if (k < 0) ...{  
                        k &= 255;  
                    }  
                    sb.append("%" + Integer.toHexString(k).toUpperCase());  
                }  
            }  
        }  
        return sb.toString();  
    }  
}  
 
   
 
   
 
注意1：Runtime类的exec()方法是在单独的进程中执行指定的字符串命令，所以得在该进程结束后，才能找到备份    的sql文件．  
 
注意2:由于是使用响应对象的getOutputStream()方法得到二进制输出流，而假如使用jsp来实现的话，由于隐含对象out的存在，很有可能导致冲突，异常的发生．所以我使用的是servlet来实现该功能．

数据库的恢复:
public static void load() {
try {
String fPath = "d:/xytx.sql";
Runtime rt = Runtime.getRuntime();

// 调用 mysql 的 cmd:
Process child = rt.exec("C:/Program Files/MySQL/MySQL Server 5.0/bin/mysql.exe -uroot -proot xytx ");
OutputStream out = child.getOutputStream();//控制台的输入信息作为输出流
String inStr;
StringBuffer sb = new StringBuffer("");
String outStr;
BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(fPath), "utf8"));
while ((inStr = br.readLine()) != null) {
sb.append(inStr + "\r\n");
}
outStr = sb.toString();

OutputStreamWriter writer = new OutputStreamWriter(out, "utf8");
writer.write(outStr);
// 注：这里如果用缓冲方式写入文件的话，会导致中文乱码，用flush()方法则可以避免
writer.flush();
// 别忘记关闭输入输出流
out.close();
br.close();
writer.close();

System.out.println("");

} catch (Exception e) {
e.printStackTrace();
}

}