QED数据库使用笔记之备份数据

本文介绍了使用QED数据库管理系统进行数据备份与恢复的方法。包括通过文件系统备份整个数据库及利用压缩XML文件进行数据导出与导入的具体步骤。此外，还提供了通过编程方式调用QED工具类实现更细粒度数据库操作的示例。

//第一种方法

QED requires zero administration. Still, sometimes you *want* to administer your data -- with QED, the database is simply a directory in the filesystem containing files accessed via a JDBC url using the QED JDBC driver. If you want, you can use file system backups (ideally when the datbase is closed, but even a snapshot of a running database should be recoverable using QED's restart logic.) to backup your database.

For more direct control over the database (as well as for a smaller backup file), QED includes the utility classes XmlDump, XmlLoad. These classes can be run from the command line:

# my handy java+qed alias :-)
alias qjava=java -classpath $QED/lib/qed.jar:$QED/lib/antlr.jar
    
# dump the db to a compressed xml file
qjava -Djdbc.url=jdbc:qed:mydb com.quadcap.sql.tools.XmlDump db.xml.gz

# reload the db from the file
rm -rf mydb
qjava '-Djdbc.url=jdbc:qed:mydb;create=true' /
      com.quadcap.sql.tools.XmlLoad db.xml.gz

//第二种方法

You can also call XmlDump/XmlLoad from your application:
import java.io.*;
import java.sql.Connection;
import com.quadcap.sql.tools.XmlDump;

void dumpDb(Connection conn, String outfile) {
    FileOutputStream fos = new FileOutputStream(outfile);
    OutputStreamWriter ow = new OutputStreamWriter(fos);
    BufferedWriter bw = new BufferedWriter(ow);
    XmlDump dump = new XmlDump(conn);
    dump.dumpTables(bw);
    bw.close();
}