Java：使用REST服务下载CSV文件
我正在尝试从REST端点下载csv文件。这就是我正在尝试的Java：使用REST服务下载CSV文件,java,spring,rest,csv,spring-mvc,Java,Spring,Rest,Csv,Spring Mvc,我正在尝试从REST端点下载csv文件。这就是我正在尝试的 @ApiOperation(value = "export", notes = "Export Cache details for a given criteria") @ApiImplicitParams({ }) @ApiResponses(value = { @ApiResponse(code = 400, message = "Bad Request"), @ApiRespons
@ApiOperation(value = "export",
notes = "Export Cache details for a given criteria")
@ApiImplicitParams({
})
@ApiResponses(value = {
@ApiResponse(code = 400, message = "Bad Request"),
@ApiResponse(code = 404, message = "Not Found"),
@ApiResponse(code = 500, message = "Internal Server Error") })
@RequestMapping(method = RequestMethod.GET, value = "/export")
public ResponseEntity export( HttpServletRequest request )
{
CacheDataManager cacheResultHandler = new CacheDataManager();
InputStreamResource inputStreamResource = null;
HttpHeaders httpHeaders = new HttpHeaders();
long contentLengthOfStream;
try
{
inputStreamResource = cacheResultHandler.exportCacheResults( request );
httpHeaders.set( HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + "test.csv" );
contentLengthOfStream = inputStreamResource.contentLength();
httpHeaders.setContentLength( contentLengthOfStream );
}
catch ( IOException e )
{
e.printStackTrace();
}
return new ResponseEntity( inputStreamResource, httpHeaders, HttpStatus.OK );
}
@Override
public InputStreamResource export( HttpServletRequest request )
{
StringBuilder sb = new StringBuilder();
StringBuilder fileName = new StringBuilder( VALIDATION_REPORT );
sb.append( "Column A" );
sb.append( "," );
sb.append( "Column B" );
sb.append( "\n" );
try
{
sb.append( "TEST A");
sb.append( ',' );
sb.append( "TEST B" );
sb.append( '\n' );
fileName.append( "_" ).append( sdf.format( new Date() ) ).append( ".csv" );
return CsvFileWriter.csvFileWrite( fileName.toString(), sb );
}
catch ( Exception e )
{
e.printStackTrace();
}
return null;
}
package it.app.ext.dashboard.util;
import org.springframework.core.io.InputStreamResource;
import java.io.*;
public class CsvFileWriter
{
public static InputStreamResource csvFileWrite( String fileName, StringBuilder content ) throws FileNotFoundException
{
File file = null;
PrintWriter pw = null;
try
{
file = new File( fileName );
pw = new PrintWriter( file );
pw.write( content.toString() );
}
catch ( FileNotFoundException e )
{
e.printStackTrace();
}
finally
{
pw.flush();
pw.close();
}
InputStream inputStream = new FileInputStream( file );
return new InputStreamResource( inputStream );
}
java.lang.IllegalStateException: InputStream has already been read - do not use InputStreamResource if a stream needs to be read multiple times.
谢谢您不要两次使用同一个文件，请使用单独的代码返回InputStream：
返回新的InputStreamResource（新文件InputStream（新文件名））不要两次使用同一文件，请使用单独的代码返回InputStream：
返回新的InputStreamResource（新文件InputStream（新文件名））解释：
您首先获得inputStream：
contentLengthOfStream=inputStreamResource.contentLength（）
然后Spring的ReturnValueHandler再次获得inputStream：
新响应属性（inputStreamResource、httpHeaders、HttpStatus.OK）
但是由inputStreamResource包装的inputStream只能使用一次：
/**
* This implementation throws IllegalStateException if attempting to
* read the underlying stream multiple times.
*/
public InputStream getInputStream() throws IOException, IllegalStateException {
if (this.read) {
throw new IllegalStateException("InputStream has already been read - " +
"do not use InputStreamResource if a stream needs to be read multiple times");
}
this.read = true;
return this.inputStream;
}
解决方案：您可以从inputStream获取字节，并返回带有字节的响应
@ApiOperation(value = "export",
notes = "Export Cache details for a given criteria")
@ApiImplicitParams({
})
@ApiResponses(value = {
@ApiResponse(code = 400, message = "Bad Request"),
@ApiResponse(code = 404, message = "Not Found"),
@ApiResponse(code = 500, message = "Internal Server Error") })
@RequestMapping(method = RequestMethod.GET, value = "/export")
public ResponseEntity export( HttpServletRequest request )
{
CacheDataManager cacheResultHandler = new CacheDataManager();
InputStreamResource inputStreamResource = null;
InputStream inputStream = null;
byte[] byteArray = new byte[0];
HttpHeaders httpHeaders = new HttpHeaders();
try
{
inputStreamResource = cacheResultHandler.exportCacheResults( request );
httpHeaders.set( HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + "test.csv" );
//convert inputStream to bytes
inputStream = inputStreamResource.getInputStream();
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead;
byte[] data = new byte[1024];
while ((nRead = inputStream.read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
}
buffer.flush();
byteArray = buffer.toByteArray();
httpHeaders.setContentLength(byteArray.length);
}
catch ( IOException e )
{
e.printStackTrace();
}
return new ResponseEntity( byteArray, httpHeaders, HttpStatus.OK );
}
建议：用于将InputStream转换为字节。需要添加库依赖项，这可以使代码简短
byte[] byteArray = IOUtils.toByteArray(inputStream);
解释：
您首先获得inputStream：
contentLengthOfStream=inputStreamResource.contentLength（）
然后Spring的ReturnValueHandler再次获得inputStream：
新响应属性（inputStreamResource、httpHeaders、HttpStatus.OK）
但是由inputStreamResource包装的inputStream只能使用一次：
/**
* This implementation throws IllegalStateException if attempting to
* read the underlying stream multiple times.
*/
public InputStream getInputStream() throws IOException, IllegalStateException {
if (this.read) {
throw new IllegalStateException("InputStream has already been read - " +
"do not use InputStreamResource if a stream needs to be read multiple times");
}
this.read = true;
return this.inputStream;
}
解决方案：您可以从inputStream获取字节，并返回带有字节的响应
@ApiOperation(value = "export",
notes = "Export Cache details for a given criteria")
@ApiImplicitParams({
})
@ApiResponses(value = {
@ApiResponse(code = 400, message = "Bad Request"),
@ApiResponse(code = 404, message = "Not Found"),
@ApiResponse(code = 500, message = "Internal Server Error") })
@RequestMapping(method = RequestMethod.GET, value = "/export")
public ResponseEntity export( HttpServletRequest request )
{
CacheDataManager cacheResultHandler = new CacheDataManager();
InputStreamResource inputStreamResource = null;
InputStream inputStream = null;
byte[] byteArray = new byte[0];
HttpHeaders httpHeaders = new HttpHeaders();
try
{
inputStreamResource = cacheResultHandler.exportCacheResults( request );
httpHeaders.set( HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + "test.csv" );
//convert inputStream to bytes
inputStream = inputStreamResource.getInputStream();
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead;
byte[] data = new byte[1024];
while ((nRead = inputStream.read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
}
buffer.flush();
byteArray = buffer.toByteArray();
httpHeaders.setContentLength(byteArray.length);
}
catch ( IOException e )
{
e.printStackTrace();
}
return new ResponseEntity( byteArray, httpHeaders, HttpStatus.OK );
}
建议：用于将InputStream转换为字节。需要添加库依赖项，这可以使代码简短
byte[] byteArray = IOUtils.toByteArray(inputStream);
我更改了这些InputStream InputStream=新文件InputStream（文件）；返回新的InputStreamResource（inputStream）；两行到你的分段。但错误与以前相同。@Rose18应创建新文件对象实例：InputStream InputStream=new FileInputStream（新文件（文件名））
而不是重复使用旧文件OJECT对不起，我不明白你说的。我需要更改哪个文件？@Rose18你可以看到我的答案，这将帮助你找到答案<代码>pw.close（）行将关闭您的文件
对象。我的意思是“文件=新文件（文件名）；”无法设置为新对象：`InputStream InputStream=新文件InputStream（文件）；`因此，请再次创建file
对象的实例：file=newfile（fileName）；InputStream InputStream=新文件InputStream（文件）；返回新的InputStreamResource（inputStream）我更改了这些InputStream InputStream=新文件InputStream（文件）；返回新的InputStreamResource（inputStream）；两行到你的分段。但错误与以前相同。@Rose18应创建新文件对象实例：InputStream InputStream=new FileInputStream（新文件（文件名））
而不是重复使用旧文件OJECT对不起，我不明白你说的。我需要更改哪个文件？@Rose18你可以看到我的答案，这将帮助你找到答案<代码>pw.close（）行将关闭您的文件
对象。我的意思是“文件=新文件（文件名）；”无法设置为新对象：`InputStream InputStream=新文件InputStream（文件）；`因此，请再次创建file
对象的实例：file=newfile（fileName）；InputStream InputStream=新文件InputStream（文件）；返回新的InputStreamResource（inputStream）此工作方式ans响应正文包含响应正文下载exportCacheResults？pr=HTL&index=0&size=100。单击此url后，它将下载应用程序八位字节流exportCacheResults pr=HTL&index=0&size=100 blob http---localhost-8080-d541c19c-6da3-478e-b8ee-0448aa5bf598的文件名。这是一个文件类型为的文件。如何下载.csv文件我看不到上面与您的url“exportCacheResults？pr=HTL&index=0&size=100”相关的任何代码。添加httpHeaders.set（“内容处置”、“附件；文件名=“+”test.csv”）
时，您可以直接下载.csv文件！这项工作ans响应正文包含响应正文下载exportCacheResults？pr=HTL&index=0&size=100。单击此url后，它将下载应用程序八位字节流exportCacheResults pr=HTL&index=0&size=100 blob http---localhost-8080-d541c19c-6da3-478e-b8ee-0448aa5bf598的文件名。这是一个文件类型为的文件。如何下载.csv文件我看不到上面与您的url“exportCacheResults？pr=HTL&index=0&size=100”相关的任何代码。添加httpHeaders.set（“内容处置”、“附件；文件名=“+”test.csv”）
时，您可以直接下载.csv文件！