SNServiceImpl.java
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package com.example.demo.service.impl;
import cn.hutool.core.codec.Base64;
import com.example.demo.exception.SNRepetitiveException;
import com.example.demo.service.SNService;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
@Service
public class SNServiceImpl implements SNService {
/**
* 多线程改写文件存在并发问题，需加锁操作
*/
private static final Lock lock = new ReentrantLock();
@Value("${SN.file.path}")
String SNFilePath;
@Value("${SN.file.temp.path}")
String SNTempFilePath;
@Override
public void addSN(String SNDto) throws SNRepetitiveException, IOException {
//加try，catch只为释放锁
try {
//加锁
lock.lock();
//读取文件，判断SN是否重复
Set<String> set = new HashSet<>();
BufferedReader bufferedReader = new BufferedReader(new FileReader(SNFilePath));
String br;
while ((br=bufferedReader.readLine()) != null) {
//截取SN
int index = br.indexOf('#');
String SN = br.substring(0,index == -1? 0 : index);
set.add(SN);
}
String addSn = SNDto.substring(0,SNDto.indexOf('#'));
if (set.contains(addSn)) {
throw new SNRepetitiveException("SN：" + addSn + " 已存在，请勿重复添加");
}
//写入
FileWriter fileWriter = new FileWriter(SNFilePath,true);
fileWriter.write(SNDto+System.lineSeparator());
fileWriter.flush();
fileWriter.close();
} finally { //释放锁
lock.unlock();
}
}
@Override
public String getEncryptSNs() throws IOException {
File file = new File(SNFilePath);
//读取文件
byte[] SNsByteArr = new byte[(int) file.length()];
FileInputStream fileInputStream = new FileInputStream(file);
fileInputStream.read(SNsByteArr);
//加密
String encodeSNs = Base64.encode(SNsByteArr);
return encodeSNs;
}
@Override
public void deleteSN(String SN) throws Exception{
try {
lock.lock();
//读取文件，记录不用删除的数据
BufferedReader bufferedReader = new BufferedReader(new FileReader(SNFilePath));
String br;
StringBuilder stringBuilder = new StringBuilder();
boolean SNExist = false;
while ((br=bufferedReader.readLine()) != null) {
//截取SN
int index = br.indexOf('#');
String str = br.substring(0,index == -1? 0 : index);
if (!SN.equals(str)) {
stringBuilder.append(br);
stringBuilder.append(System.lineSeparator());
} else {
SNExist = true;
}
}
bufferedReader.close();
//如果存在要删除的SN，先将数据备份，再将留存数据覆盖掉原SN文件，避免数据写一半断电丢失。
if (SNExist) {
//备份数据
FileWriter SNTempfileWriter = new FileWriter(SNTempFilePath);
SNTempfileWriter.write(stringBuilder.toString());
SNTempfileWriter.flush();
SNTempfileWriter.close();
//覆盖掉原来的数据到SN文件中
FileWriter SNfileWriter = new FileWriter(SNFilePath);
SNfileWriter.write(stringBuilder.toString());
SNfileWriter.flush();
SNfileWriter.close();
}
} finally {
lock.unlock();
}
}
@Override
public void downloadSNFile(HttpServletRequest request, HttpServletResponse response) throws IOException {
File file = new File(SNFilePath);
response.setCharacterEncoding("UTF-8");
response.setHeader("Content-type","application/octet-stream;charset=UTF-8");
response.setHeader("Content-Disposition", "attachment;filename=" + java.net.URLEncoder.encode(file.getName().trim(), "UTF-8"));
response.addHeader("Pargam", "no-cache");
response.addHeader("Cache-Control", "no-cache");
//读取文件
byte[] SNsByteArr = new byte[(int) file.length()];
FileInputStream fileInputStream = new FileInputStream(file);
fileInputStream.read(SNsByteArr);
//加密
String encodeSNs = Base64.encode(SNsByteArr);
//写入到输出流
response.addHeader("Content-Length",String.valueOf(encodeSNs.getBytes().length));
OutputStream outputStream = response.getOutputStream();
outputStream.write(encodeSNs.getBytes());
outputStream.flush();
outputStream.close();
}
}