如何在java中从jar下载已有的xlsx文件

Question

我把Excel文件放在resources/template/a.xlsx中，我把它和mvn package打包，我想和一个API从这个jar下载.xlsx。

我的API：

public void downloadExcelTemplate(RoutingContext routingContext) {
String fileName = "a.xlsx";
String path = "template" + File.separator+fileName;
HttpServerResponse response = routingContext.response();
try {
BufferedReader in = new BufferedReader(new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream(path)));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = in.readLine()) != null){
buffer.append(line);
}
response.putHeader("content-type", "application/octet-stream;charset=UTF-8");
response.putHeader("Content-Disposition", "attachment;filename=" + new String(fileName.getBytes(), StandardCharsets.ISO_8859_1));
response.putHeader("Pragma", "no-cache");
response.putHeader("Cache-Control", "no-cache");
response.setChunked(true);
response.write(buffer.toString());
} catch (IOException e) {
logger.error("error： ", e);
}
response.end();
}

我使用vertx.web和Spring，poi依赖项是：

<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>3.17</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml-schemas</artifactId>
<version>3.17-beta1</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>3.17-beta1</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-excelant</artifactId>
<version>3.17-beta1</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-scratchpad</artifactId>
<version>3.17-beta1</version>
</dependency>

我认为SpringMVC和vertx.web在下载时是一样的，但当我尝试下载时，下载的xlsx文件无法打开。

Answer 1

在这种情况下，不要使用java.io.Reader！

xlsx文件是二进制的(从技术上讲，它们是zip文件(。

使用读卡器会损坏数据

public void downloadExcelTemplate(RoutingContext routingContext) {
String fileName = "a.xlsx";
String path = "template" + File.separator+fileName;
HttpServerResponse response = routingContext.response();
try(final InputStream inputStream = 
this.getClass().getClassLoader().getResourceAsStream(path);
final BufferedInputStream in =
new BufferedInputStream(inputStream); ) {
// Use the actual content type for the file
response.putHeader("content-type", 
"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
response.putHeader("Content-Disposition", 
"attachment;filename=" + 
new String(fileName.getBytes(), StandardCharsets.ISO_8859_1));
response.putHeader("Pragma", "no-cache");
response.putHeader("Cache-Control", "no-cache");
response.setChunked(true);
// Vert.x Buffer Object
Buffer buffer = Buffer.buffer()
byte[] rawBuffer = new byte[1024];
int numRead;
while((numRead = is.read(rawBuffer, 0, rawBuffer.length)) != -1) {
response.appendBytes(rawBuffer, 0, numRead);
}
response.write(buffer);
} catch (IOException e) {
logger.error("error： ", e);
}
response.end();
}
}

Answer 2

资源路径区分大小写，并使用斜线(/(作为路径分隔符。

响应是一个二进制文件，而不是文本。因此，它必须由InputStream加载，并由OutputStream编写。读写器支持Unicode文本，并且总是暗示二进制字节的字符集转换。这会破坏事物，或者至少会使它们变慢。

public void downloadExcelTemplate(RoutingContext routingContext) {
String fileName = "a.xlsx";
String path = "template/" + fileName;
HttpServerResponse response = routingContext.response();
try {
URL url = getClass().getClassLoader().getResource(path);
Path path = Paths.get(url.toURI());
response.putHeader("Content-Type", "application/octet-stream;charset=UTF-8");
response.putHeader("Content-Disposition",
"attachment;filename=" + URLEncoder.encode(fileName,"ISO-8859-1"));
response.putHeader("Pragma", "no-cache");
response.putHeader("Cache-Control", "no-cache");
response.setChunked(true);
// It would have been nice to do just: Files.copy(path, response.getOutputStream());
byte[] content = Files.readAllBytes(path);
Buffer buffer = Buffer.buffer(content);
response.write(buffer);
} catch (IOException e) {
logger.error("error： ", e);
}
response.end();
}

不确定"；；charset＝UTF-8"；用于内容类型。Excel内部使用UTF-8？不应该被需要。

Answer 3

很高兴回复您。首先，您应该将MVN包视为导致excel无法打开的罐子。

然后，您可以尝试其他源路径进行访问。

最后，您可以尝试在jar的同一文件目录中拍摄excel以进行访问。我认为这没关系。我向你问好。Allen