JAVA导出CSV文件实例教程

以前导出总是用POI导出为Excel文件，后来当我了解到CSV以后，我发现速度飞快。

如果导出的数据不要求格式、样式、公式等等，建议最好导成CSV文件，因为真的很快。

虽然我们可以用Java再带的文件相关的类去操作以生成一个CSV文件，但事实上有好多第三方类库也提供了类似的功能。

这里我们使用apache提供的commons-csv组件

Commons CSV

文档在这里

http://commons.apache.org/

http://commons.apache.org/proper/commons-csv/

http://commons.apache.org/proper/commons-csv/user-guide.html

先看一下具体用法

@Test public void testWrite() throws Exception {
  FileOutputStream fos = new FileOutputStream("E:/cjsworkspace/cjs-excel-demo/target/abc.csv");
  OutputStreamWriter osw = new OutputStreamWriter(fos, "GBK");

  CSVFormat csvFormat = CSVFormat.DEFAULT.withHeader("姓名", "年龄", "家乡");
  CSVPrinter csvPrinter = new CSVPrinter(osw, csvFormat);//  csvPrinter = CSVFormat.DEFAULT.withHeader("姓名", "年龄", "家乡").print(osw);

  for (int i = 0; i < 10; i++) {
   csvPrinter.printRecord("张三", 20, "湖北");
  }

  csvPrinter.flush();
  csvPrinter.close();

 }

 @Test public void testRead() throws IOException {
  InputStream is = new FileInputStream("E:/cjsworkspace/cjs-excel-demo/target/abc.csv");
  InputStreamReader isr = new InputStreamReader(is, "GBK");
  Reader reader = new BufferedReader(isr);

  CSVParser parser = CSVFormat.EXCEL.withHeader("name", "age", "jia").parse(reader);//  CSVParser csvParser = CSVParser.parse(reader, CSVFormat.DEFAULT.withHeader("name", "age", "jia"));
  List<CSVRecord> list = parser.getRecords();  for (CSVRecord record : list) {
   System.out.println(record.getRecordNumber()     + ":" + record.get("name")     + ":" + record.get("age")     + ":" + record.get("jia"));
  }

  parser.close();
 } /**
  * Parsing an Excel CSV File  */
 @Test public void testParse() throws Exception {
  Reader reader = new FileReader("C:/Users/Administrator/Desktop/abc.csv");
  CSVParser parser = CSVFormat.EXCEL.parse(reader);  for (CSVRecord record : parser.getRecords()) {
   System.out.println(record);
  }
  parser.close();
 } /**
  * Defining a header manually  */
 @Test public void testParseWithHeader() throws Exception {
  Reader reader = new FileReader("C:/Users/Administrator/Desktop/abc.csv");
  CSVParser parser = CSVFormat.EXCEL.withHeader("id", "name", "code").parse(reader);  for (CSVRecord record : parser.getRecords()) {
   System.out.println(record.get("id") + ","
     + record.get("name") + ","
     + record.get("code"));
  }
  parser.close();
 } /**
  * Using an enum to define a header  */
 enum MyHeaderEnum {
  ID, NAME, CODE;
 }

 @Test public void testParseWithEnum() throws Exception {
  Reader reader = new FileReader("C:/Users/Administrator/Desktop/abc.csv");
  CSVParser parser = CSVFormat.EXCEL.withHeader(MyHeaderEnum.class).parse(reader);  for (CSVRecord record : parser.getRecords()) {
   System.out.println(record.get(MyHeaderEnum.ID) + ","
     + record.get(MyHeaderEnum.NAME) + ","
     + record.get(MyHeaderEnum.CODE));
  }
  parser.close();
 } private List<Map<String, String>> recordList = new ArrayList<>();

 @Before public void init() {  for (int i = 0; i < 5; i++) {
   Map<String, String> map = new HashMap<>();
   map.put("name", "zhangsan");
   map.put("code", "001");
   recordList.add(map);
  }
 }

 @Test public void writeMuti() throws InterruptedException {
  ExecutorService executorService = Executors.newFixedThreadPool(3);
  CountDownLatch doneSignal = new CountDownLatch(2);

  executorService.submit(new exprotThread("E:/0.csv", recordList, doneSignal));
  executorService.submit(new exprotThread("E:/1.csv", recordList, doneSignal));

  doneSignal.await();
  System.out.println("Finish!!!");
 } class exprotThread implements Runnable {  private String filename;  private List<Map<String, String>> list;  private CountDownLatch countDownLatch;  public exprotThread(String filename, List<Map<String, String>> list, CountDownLatch countDownLatch) {   this.filename = filename;   this.list = list;   this.countDownLatch = countDownLatch;
  }

  @Override  public void run() {   try {
    CSVPrinter printer = new CSVPrinter(new FileWriter(filename), CSVFormat.EXCEL.withHeader("NAME", "CODE"));    for (Map<String, String> map : list) {
     printer.printRecord(map.values());
    }
    printer.close();
    countDownLatch.countDown();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
 }

CSV与EXCEL

　　/**
  * 测试写100万数据需要花费多长时间  */
 @Test public void testMillion() throws Exception {  int times = 10000 * 10;
  Object[] cells = {"满100减15元", "100011", 15};  // 导出为CSV文件
  long t1 = System.currentTimeMillis();
  FileWriter writer = new FileWriter("G:/test1.csv");
  CSVPrinter printer = CSVFormat.EXCEL.print(writer);  for (int i = 0; i < times; i++) {
   printer.printRecord(cells);
  }
  printer.flush();
  printer.close();  long t2 = System.currentTimeMillis();
  System.out.println("CSV: " + (t2 - t1));  // 导出为Excel文件
  long t3 = System.currentTimeMillis();
  XSSFWorkbook workbook = new XSSFWorkbook();
  XSSFSheet sheet = workbook.createSheet();  for (int i = 0; i < times; i++) {
   XSSFRow row = sheet.createRow(i);   for (int j = 0; j < cells.length; j++) {
    XSSFCell cell = row.createCell(j);
    cell.setCellValue(String.valueOf(cells[j]));
   }
  }
  FileOutputStream fos = new FileOutputStream("G:/test2.xlsx");
  workbook.write(fos);
  fos.flush();
  fos.close();  long t4 = System.currentTimeMillis();
  System.out.println("Excel: " + (t4 - t3));
 }

Maven依赖

<dependencies>
 <dependency>
  <groupId>org.apache.commons</groupId>
  <artifactId>commons-csv</artifactId>
  <version>1.5</version>
 </dependency>

 <dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi</artifactId>
  <version>3.17</version>
 </dependency>

 <dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi-ooxml</artifactId>
  <version>3.17</version>
 </dependency>

 <dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.12</version>
  <scope>test</scope>
 </dependency></dependencies>

最后，刚才的例子中只写了3个字段，100万行，生成的CSV文件有十几二十兆，太多的话建议分多个文件打包下周，不然想象一个打开一个几百兆的excel都费劲。

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