【Java-IO】Java常用IO流操作实现本地文件的读写

电玩女神 2023-10-13 13:12 89阅读 0赞

下面示例包括使用 `BufferedReader` 读，`FileWriter`、`FileOutputStream` 写。

package gaei.cn.x5l.x5lhive2cos.utils;
    
    import java.io.*;
    
    //历史数据自动生成sql修复分区
    public class HdfsTboxAddPartitionSql {
        
        public static void main(String[] args) {
        
            String dbName = "database";
            String tableName = "table_name";
            String filePathInput = "C:/Users/MECHREVO/Desktop/新建文件夹/history_partitions/分区详情/" + tableName + ".txt";
            String filePathOutput = "C:/Users/MECHREVO/Desktop/新建文件夹/history_partitions/分区修改至s3-sql/" + tableName + ".txt";
            File fileIn = new File(filePathInput);
            File fileOut = new File(filePathOutput);
            BufferedReader reader = null;
            FileWriter fw = null;
    //        FileOutputStream fos = null;
            String partitionDir = null;
            int line = 1;
            try {
        
                reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileIn), "GBK"));
                fw = new FileWriter(fileOut);
    //            fos = new FileOutputStream(fileOut);
                while ((partitionDir = reader.readLine()) != null) {
        
                    StringBuilder alterSql = new StringBuilder();
                    alterSql.append("alter table ");
                    String sampleDateDir = partitionDir.split("/")[0];//sample_date=20230510
                    String partitionNameDir = partitionDir.split("/")[1];//partition_name=101
                    String sample_date = sampleDateDir.split("=")[0];//sample_date
                    String sample_date_yyyyMMdd = sampleDateDir.split("=")[1];//20230510
                    String partition_name = partitionNameDir.split("=")[0];//partition_name
                    String partition_name_num = partitionNameDir.split("=")[1];//100
                    alterSql.append(dbName)
                            .append(".")
                            .append(tableName)
                            .append(" add if not exists partition(")
                            .append(sample_date)
                            .append("='")
                            .append(sample_date_yyyyMMdd)
                            .append("', ")
                            .append(partition_name)
                            .append("='")
                            .append(partition_name_num)
                            .append("') ")
                            .append("location '")
    //                        .append("hdfs://prdns/warehouse/tablespace/external/hive/ods_x5l.db/")
                            .append("s3a://buceketname/prd/data/")
                            .append(dbName)
                            .append("/")
                            .append(tableName)
                            .append("/")
                            .append(partitionDir)
                            .append("';");
                    fw.write(alterSql + "\n");
    //                fos.write((alterSql + "\n").getBytes());
                    System.out.println(alterSql);
                    line++;
                }
                fw.flush();
                fw.close();
    //            fos.flush();
    //            fos.close();
                reader.close();
            } catch (FileNotFoundException e) {
        
                e.printStackTrace();
            } catch (IOException e) {
        
                e.printStackTrace();
            } finally {
        
                if (reader != null) {
        
                    try {
        
                        fw.close();
    //                    fos.flush();
    //                    fos.close();
                        reader.close();
                    } catch (IOException e) {
        
                        e.printStackTrace();
                    }
                }
            }
        }
    }