华为openGauss 示例-通过本地文件导入导出数据

在使用JAVA语言基于openGauss进行二次开发时，可以使用CopyManager接口，通过流方式，将数据库中的数据导出到本地文件或者将本地文件导入数据库中，文件格式支持CSV、TEXT等格式。

样例程序如下，执行时需要加载openGauss jdbc驱动。

``` 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/postgres"); //数据库URL 
  String username = new String("jack");            //用户名 
  String password = new String("Gauss@123");             //密码 
  String tablename = new String("migration_table"); //定义表信息 
  String tablename1 = new String("migration_table_1"); //定义表信息 
  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); 
      }
  // 将SELECT * FROM migration_table查询结果导出到本地文件d:/data.txt  
  try {
 copyToFile(conn, "d:/data.txt", "(SELECT * FROM migration_table)");

} catch (SQLException e) { k e.printStackTrace(); } catch (IOException e) {

e.printStackTrace(); }
//将d:/data.txt中的数据导入到migration_table_1中。 try { copyFromFile(conn, "d:/data.txt", tablename1); } catch (SQLException e) { e.printStackTrace(); } catch (IOException e) {

e.printStackTrace(); }

  // 将migration_table_1中的数据导出到本地文件d:/data1.txt  
  try {
  copyToFile(conn, "d:/data1.txt", tablename1);

} catch (SQLException e) {

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

e.printStackTrace(); }
} // 使用copyIn把数据从文件中导入数据库， 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();  
         }  
     }  
 }

}

// 使用copyOut把数据从数据库中导出到文件中 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();  
          }  
      }  
  }

}
} ```