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更新时间：2024-11-26 GMT+08:00
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JDBC中使用COPY命令导出导入数据

操作场景

使用Java语言开发应用程序时，通过调用JDBC驱动的CopyManager接口，从文件或其他数据库向GaussDB写入数据。

示例1：通过本地文件导出导入数据

调用JDBC驱动的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GaussDB的JDBC驱动。

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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://localhost:8000/postgres"); //数据库URL 
      String username = System.getenv("EXAMPLE_USERNAME_ENV");    //用户名
      String password = System.getenv("EXAMPLE_PASSWORD_ENV");    //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); 
      } 
      
      // 将表migration_table中数据导出到本地文件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();
      }    
      //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) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }  

      // 将表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) {
          // 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();  
              }  
          }  
      }  
  }  
}

示例2：从B迁移数据

下面示例演示如何通过CopyManager从B向GaussDB进行数据迁移的过程。

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import java.io.StringReader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import org.postgresql.copy.CopyManager;
import org.postgresql.core.BaseConnection;

public class Migration{

    public static void main(String[] args) {
        String url = new String("jdbc:postgresql://localhost:8000/postgres"); //数据库URL 
        String user = new String("username");            //GaussDB数据库用户名 
        String pass = new String("passwd");             //GaussDB数据库密码 
        String tablename = new String("migration_table_1"); //定义表信息 
        String delimiter = new String("|");              //定义分隔符 
        String encoding = new String("UTF8");            //定义字符集 
        String driver = "org.postgresql.Driver";
        StringBuffer buffer = new StringBuffer();       //定义存放格式化数据的缓存 

        try {
            //获取源数据库查询结果集 
            ResultSet rs = getDataSet();

            //遍历结果集，逐行获取记录 
            //将每条记录中各字段值，按指定分隔符分割，由换行符结束，拼成一个字符串 
            //把拼成的字符串，添加到缓存buffer 
            while (rs.next()) {
                buffer.append(rs.getString(1) + delimiter
                        + rs.getString(2) + delimiter
                        + rs.getString(3) + delimiter
                        + rs.getString(4)
                        + "\n");
            }
            rs.close();

            try {
                //建立目标数据库连接 
                Class.forName(driver);
                Connection conn = DriverManager.getConnection(url, user, pass);
                BaseConnection baseConn = (BaseConnection) conn;
                baseConn.setAutoCommit(false);

                //初始化表信息   
                String sql = "Copy " + tablename + " from STDIN with (DELIMITER " + "'" + delimiter + "'" +","+ " ENCODING " + "'" + encoding + "')";

                //提交缓存buffer中的数据                   
                CopyManager cp = new CopyManager(baseConn);
                StringReader reader = new StringReader(buffer.toString());
                cp.copyIn(sql, reader);
                baseConn.commit();
                reader.close();
                baseConn.close();
            } catch (ClassNotFoundException e) {
                e.printStackTrace(System.out);
            } catch (SQLException e) {
                e.printStackTrace(System.out);
            }

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

    //******************************** 
    // 从源数据库返回查询结果集     
    //********************************* 
    private static ResultSet getDataSet() {
        ResultSet rs = null;
        try {
            Class.forName("com.B.jdbc.Driver").newInstance();
            Connection conn = DriverManager.getConnection("jdbc:MY://10.119.179.227:3306/jack?useSSL=false&allowPublicKeyRetrieval=true", "jack", "xxxxxxxxx");
            Statement stmt = conn.createStatement();
            rs = stmt.executeQuery("select * from migration_table");
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return rs;
    }
}

相关链接

有关CopyManager的更多信息，请参见：

父主题： 数据库迁移

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