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
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@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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