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

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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