Updated at: 2022-08-03 GMT+08:00

Example: Importing and Exporting Data Through Local Files

When the JAVA language is used for secondary development based on GaussDB(DWS), you can use the CopyManager interface to export data from the database to a local file or import a local file to the database by streaming. The file can be in CSV or TEXT format.

The sample program is as follows. Load the GaussDB(DWS) JDBC driver before running it.

//gsjdbc4.jar is used as an example. If gsjdbc200.jar is used, replace the class name org.postgresql with com.huawei.gauss200.jdbc and replace the URL prefix jdbc:postgresql with jdbc:gaussdb. import java.sql.Connection; import java.sql.DriverManager; import java.io.IOException; import java.io.FileInputStream; import java.io.FileOutputStream; import java.sql.SQLException; import org.postgresql.copy.CopyManager; import org.postgresql.core.BaseConnection; public class Copy{ public static void main(String[] args) { String urls = new String("jdbc:postgresql://10.180.155.74:8000/gaussdb"); //Database URL String username = new String("jack"); //Username String password = new String("********"); // Password String tablename = new String("migration_table"); //Define table information. String tablename1 = new String("migration_table_1"); //Define table information. String driver = "org.postgresql.Driver"; Connection conn = null; try { Class.forName(driver); conn = DriverManager.getConnection(urls, username, password); } catch (ClassNotFoundException e) { e.printStackTrace(System.out); } catch (SQLException e) { e.printStackTrace(System.out); } //Export the query result of SELECT * FROM migration_table to the local file d:/data.txt. try { copyToFile(conn, "d:/data.txt", "(SELECT * FROM migration_table)"); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } //Import data from the d:/data.txt file to the migration_table_1 table. try { copyFromFile(conn, "d:/data.txt", tablename1); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } //Export the data from the migration_table_1 table to the d:/data1.txt file. try { copyToFile(conn, "d:/data1.txt", tablename1); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static void copyFromFile(Connection connection, String filePath, String tableName) throws SQLException, IOException { FileInputStream fileInputStream = null; try { CopyManager copyManager = new CopyManager((BaseConnection)connection); fileInputStream = new FileInputStream(filePath); copyManager.copyIn("COPY " + tableName + " FROM STDIN", fileInputStream); } finally { if (fileInputStream != null) { try { fileInputStream.close(); } catch (IOException e) { e.printStackTrace(); } } } } public static void copyToFile(Connection connection, String filePath, String tableOrQuery) throws SQLException, IOException { FileOutputStream fileOutputStream = null; try { CopyManager copyManager = new CopyManager((BaseConnection)connection); fileOutputStream = new FileOutputStream(filePath); copyManager.copyOut("COPY " + tableOrQuery + " TO STDOUT", fileOutputStream); } finally { if (fileOutputStream != null) { try { fileOutputStream.close(); } catch (IOException e) { e.printStackTrace(); } } } } }
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