Java : InputStream to Multi-part file conversion, 结果文件为空
Java : InputStream to Multi-part file conversion, result file is empty
我正在开发一个 Java 应用程序，我试图在其中从下载的 InputStream 创建一个多部分文件。不幸的是，它不工作，Multipart 文件是空的。在将其复制到 Multipart 之前，我检查了磁盘上 savedFile 的大小，它具有正确的大小、属性和内容。
我在转换中做错了什么，没有堆栈跟踪，因为我正在捕捉它。
代码：
// InputStream contains file data.
byte[] bytes = IOUtils.toByteArray(inputStream);
File file = new File(msg + "temp");
if (file.exists() && file.isDirectory()) {
OutputStream outputStream = new FileOutputStream(new File(msg + "temp" + "/" +
groupAttachments.getFileName()));
outputStream.write(bytes);
outputStream.close();
}
java.io.File savedFile = new java.io.File(msg + "temp" + "/" +
groupAttachments.getFileName());
DiskFileItem fileItem = new DiskFileItem("file", "text/plain", false,
savedFile.getName(), (int) savedFile.length(), savedFile.getParentFile());
fileItem.getOutputStream();
MultipartFile multipartFile = new CommonsMultipartFile(fileItem);
System.out.println("Saved file size is "+savedFile.length());
if (multipartFile.isEmpty()) {
System.out.println("Dropbox uploaded multipart file is empty");
} else {
System.out.println("Multipart file is not empty.");
}
this.dropboxTask.insertFile(multipartFile, "",
savedPersonalNoteObject.getNoteid(), (long) 0, true);
Path path = Paths.get(msg + "temp" + "/" + groupAttachments.getFileName());
控制台输出：
Multipart file is not empty
Bytes are not null
File path is /My Group
Input stream is not null
Saved file size is 4765
Dropbox uploaded multipart file is empty
Multipart file is empty
Bytes are not null
我在转换过程中做错了什么？你能帮忙的话，我会很高兴。非常感谢。
DiskFileItem 使用 DeferredFileOutputStream，它使用内存中的字节数组，仅在实际传输字节时才填充。
由于直接使用文件，实际上没有复制任何字节，
字节数组永远不会被填充。自己看源码：
源代码CommonsMultipartFile
源代码DiskFileItem
源代码DeferredFileOutputStream
因此，不只是调用 fileItem.getOutputStream();，而是传输字节以填充内存中的字节数组：
try (OutputStream out = fileItem.getOutputStream();
InputStream in = Files.newInputStream(file.toPath())) {
IOUtils.copy(in, dfos);
}
然后 tranferTo 调用将起作用。
对于只移动一个文件来说，这似乎有点麻烦：CommonsMultipartFile 只在 transferTo 方法中调用 fileItem.write((File)dest)。
下面是两个测试用例，一个使用 DiskFileItem，一个使用 LocalFileItem。 LocalFileItem 的代码如下所示。
我使用了依赖项 org.springframework:spring-web:4.2.2.RELEASE、commons-fileupload:commons-fileupload:1.3.1 和 junit:junit:4.12
测试classCommonMp:
import static org.junit.Assert.*;
import java.io.*;
import java.nio.charset.*;
import java.nio.file.*;
import org.apache.commons.fileupload.disk.DiskFileItem;
import org.apache.commons.io.IOUtils;
import org.junit.Test;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
public class CommonMp {
private final Charset CS = StandardCharsets.UTF_8;
@Test
public void testLocalMp() {
Path testInputFile = null, testOutputFile = null;
try {
testInputFile = prepareInputFile();
LocalFileItem lfi = new LocalFileItem(testInputFile);
CommonsMultipartFile cmf = new CommonsMultipartFile(lfi);
System.out.println("Empty: " + cmf.isEmpty());
testOutputFile = testInputFile.getParent().resolve("testMpOutput.txt");
cmf.transferTo(testOutputFile.toFile());
System.out.println("Size: " + cmf.getSize());
printOutput(testOutputFile);
} catch (Exception e) {
e.printStackTrace();
fail();
} finally {
deleteSilent(testInputFile, testOutputFile);
}
}
@Test
public void testMp() {
Path testInputFile = null, testOutputFile = null;
try {
testInputFile = prepareInputFile();
DiskFileItem di = new DiskFileItem("file", "text/plain", false, testInputFile.getFileName().toString(),
(int) Files.size(testInputFile), testInputFile.getParent().toFile());
try (OutputStream out = di.getOutputStream();
InputStream in = Files.newInputStream(testInputFile)) {
IOUtils.copy(in, out);
}
CommonsMultipartFile cmf = new CommonsMultipartFile(di);
System.out.println("Size: " + cmf.getSize());
testOutputFile = testInputFile.getParent().resolve("testMpOutput.txt");
cmf.transferTo(testOutputFile.toFile());
printOutput(testOutputFile);
} catch (Exception e) {
e.printStackTrace();
fail();
} finally {
deleteSilent(testInputFile, testOutputFile);
}
}
private Path prepareInputFile() throws IOException {
Path tmpDir = Paths.get(System.getProperty("java.io.tmpdir"));
Path testInputFile = tmpDir.resolve("testMpinput.txt");
try (OutputStream out = Files.newOutputStream(testInputFile)){
out.write("Just a test.".getBytes(CS));
}
return testInputFile;
}
private void printOutput(Path p) throws IOException {
byte[] outBytes = Files.readAllBytes(p);
System.out.println("Output: " + new String(outBytes, CS));
}
private void deleteSilent(Path... paths) {
for (Path p : paths) {
try { if (p != null) p.toFile().delete(); } catch (Exception ignored) {}
}
}
}
自定义LocalFileItemclass,YMMV!
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemHeaders;
public class LocalFileItem implements FileItem {
private static final long serialVersionUID = 2467880290855097332L;
private final Path localFile;
public LocalFileItem(Path localFile) {
this.localFile = localFile;
}
@Override
public void write(File file) throws Exception {
Files.move(localFile, file.toPath(), StandardCopyOption.REPLACE_EXISTING);
}
@Override
public long getSize() {
// Spring's CommonsMultipartFile caches the file size and uses it to determine availability.
long size = -1L;
try {
size = Files.size(localFile);
} catch (IOException ignored) {}
return size;
}
@Override
public void delete() {
localFile.toFile().delete();
}
/* *** properties and unsupported methods *** */
private FileItemHeaders headers;
private String contentType;
private String fieldName;
private boolean formField;
@Override
public FileItemHeaders getHeaders() {
return headers;
}
@Override
public void setHeaders(FileItemHeaders headers) {
this.headers = headers;
}
@Override
public InputStream getInputStream() throws IOException {
throw new IOException("Only method write(File) is supported.");
}
public void setContentType(String contentType) {
this.contentType = contentType;
}
@Override
public String getContentType() {
return contentType;
}
@Override
public String getName() {
return localFile.getFileName().toString();
}
@Override
public boolean isInMemory() {
return false;
}
@Override
public byte[] get() {
throw new RuntimeException("Only method write(File) is supported.");
}
@Override
public String getString(String encoding)
throws UnsupportedEncodingException {
throw new RuntimeException("Only method write(File) is supported.");
}
@Override
public String getString() {
throw new RuntimeException("Only method write(File) is supported.");
}
@Override
public String getFieldName() {
return fieldName;
}
@Override
public void setFieldName(String name) {
this.fieldName = name;
}
@Override
public boolean isFormField() {
return formField;
}
@Override
public void setFormField(boolean state) {
this.formField = state;
}
@Override
public OutputStream getOutputStream() throws IOException {
throw new IOException("Only method write(File) is supported.");
}
}
我正在开发一个 Java 应用程序，我试图在其中从下载的 InputStream 创建一个多部分文件。不幸的是，它不工作，Multipart 文件是空的。在将其复制到 Multipart 之前，我检查了磁盘上 savedFile 的大小，它具有正确的大小、属性和内容。
我在转换中做错了什么，没有堆栈跟踪，因为我正在捕捉它。
代码：
// InputStream contains file data.
byte[] bytes = IOUtils.toByteArray(inputStream);
File file = new File(msg + "temp");
if (file.exists() && file.isDirectory()) {
OutputStream outputStream = new FileOutputStream(new File(msg + "temp" + "/" +
groupAttachments.getFileName()));
outputStream.write(bytes);
outputStream.close();
}
java.io.File savedFile = new java.io.File(msg + "temp" + "/" +
groupAttachments.getFileName());
DiskFileItem fileItem = new DiskFileItem("file", "text/plain", false,
savedFile.getName(), (int) savedFile.length(), savedFile.getParentFile());
fileItem.getOutputStream();
MultipartFile multipartFile = new CommonsMultipartFile(fileItem);
System.out.println("Saved file size is "+savedFile.length());
if (multipartFile.isEmpty()) {
System.out.println("Dropbox uploaded multipart file is empty");
} else {
System.out.println("Multipart file is not empty.");
}
this.dropboxTask.insertFile(multipartFile, "",
savedPersonalNoteObject.getNoteid(), (long) 0, true);
Path path = Paths.get(msg + "temp" + "/" + groupAttachments.getFileName());
控制台输出：
Multipart file is not empty
Bytes are not null
File path is /My Group
Input stream is not null
Saved file size is 4765
Dropbox uploaded multipart file is empty
Multipart file is empty
Bytes are not null
我在转换过程中做错了什么？你能帮忙的话，我会很高兴。非常感谢。
DiskFileItem 使用 DeferredFileOutputStream，它使用内存中的字节数组，仅在实际传输字节时才填充。
由于直接使用文件，实际上没有复制任何字节，
字节数组永远不会被填充。自己看源码：
源代码CommonsMultipartFile
源代码DiskFileItem
源代码DeferredFileOutputStream
因此，不只是调用 fileItem.getOutputStream();，而是传输字节以填充内存中的字节数组：
try (OutputStream out = fileItem.getOutputStream();
InputStream in = Files.newInputStream(file.toPath())) {
IOUtils.copy(in, dfos);
}
然后 tranferTo 调用将起作用。
对于只移动一个文件来说，这似乎有点麻烦：CommonsMultipartFile 只在 transferTo 方法中调用 fileItem.write((File)dest)。
下面是两个测试用例，一个使用 DiskFileItem，一个使用 LocalFileItem。 LocalFileItem 的代码如下所示。
我使用了依赖项 org.springframework:spring-web:4.2.2.RELEASE、commons-fileupload:commons-fileupload:1.3.1 和 junit:junit:4.12
测试classCommonMp:
import static org.junit.Assert.*;
import java.io.*;
import java.nio.charset.*;
import java.nio.file.*;
import org.apache.commons.fileupload.disk.DiskFileItem;
import org.apache.commons.io.IOUtils;
import org.junit.Test;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
public class CommonMp {
private final Charset CS = StandardCharsets.UTF_8;
@Test
public void testLocalMp() {
Path testInputFile = null, testOutputFile = null;
try {
testInputFile = prepareInputFile();
LocalFileItem lfi = new LocalFileItem(testInputFile);
CommonsMultipartFile cmf = new CommonsMultipartFile(lfi);
System.out.println("Empty: " + cmf.isEmpty());
testOutputFile = testInputFile.getParent().resolve("testMpOutput.txt");
cmf.transferTo(testOutputFile.toFile());
System.out.println("Size: " + cmf.getSize());
printOutput(testOutputFile);
} catch (Exception e) {
e.printStackTrace();
fail();
} finally {
deleteSilent(testInputFile, testOutputFile);
}
}
@Test
public void testMp() {
Path testInputFile = null, testOutputFile = null;
try {
testInputFile = prepareInputFile();
DiskFileItem di = new DiskFileItem("file", "text/plain", false, testInputFile.getFileName().toString(),
(int) Files.size(testInputFile), testInputFile.getParent().toFile());
try (OutputStream out = di.getOutputStream();
InputStream in = Files.newInputStream(testInputFile)) {
IOUtils.copy(in, out);
}
CommonsMultipartFile cmf = new CommonsMultipartFile(di);
System.out.println("Size: " + cmf.getSize());
testOutputFile = testInputFile.getParent().resolve("testMpOutput.txt");
cmf.transferTo(testOutputFile.toFile());
printOutput(testOutputFile);
} catch (Exception e) {
e.printStackTrace();
fail();
} finally {
deleteSilent(testInputFile, testOutputFile);
}
}
private Path prepareInputFile() throws IOException {
Path tmpDir = Paths.get(System.getProperty("java.io.tmpdir"));
Path testInputFile = tmpDir.resolve("testMpinput.txt");
try (OutputStream out = Files.newOutputStream(testInputFile)){
out.write("Just a test.".getBytes(CS));
}
return testInputFile;
}
private void printOutput(Path p) throws IOException {
byte[] outBytes = Files.readAllBytes(p);
System.out.println("Output: " + new String(outBytes, CS));
}
private void deleteSilent(Path... paths) {
for (Path p : paths) {
try { if (p != null) p.toFile().delete(); } catch (Exception ignored) {}
}
}
}
自定义LocalFileItemclass,YMMV!
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemHeaders;
public class LocalFileItem implements FileItem {
private static final long serialVersionUID = 2467880290855097332L;
private final Path localFile;
public LocalFileItem(Path localFile) {
this.localFile = localFile;
}
@Override
public void write(File file) throws Exception {
Files.move(localFile, file.toPath(), StandardCopyOption.REPLACE_EXISTING);
}
@Override
public long getSize() {
// Spring's CommonsMultipartFile caches the file size and uses it to determine availability.
long size = -1L;
try {
size = Files.size(localFile);
} catch (IOException ignored) {}
return size;
}
@Override
public void delete() {
localFile.toFile().delete();
}
/* *** properties and unsupported methods *** */
private FileItemHeaders headers;
private String contentType;
private String fieldName;
private boolean formField;
@Override
public FileItemHeaders getHeaders() {
return headers;
}
@Override
public void setHeaders(FileItemHeaders headers) {
this.headers = headers;
}
@Override
public InputStream getInputStream() throws IOException {
throw new IOException("Only method write(File) is supported.");
}
public void setContentType(String contentType) {
this.contentType = contentType;
}
@Override
public String getContentType() {
return contentType;
}
@Override
public String getName() {
return localFile.getFileName().toString();
}
@Override
public boolean isInMemory() {
return false;
}
@Override
public byte[] get() {
throw new RuntimeException("Only method write(File) is supported.");
}
@Override
public String getString(String encoding)
throws UnsupportedEncodingException {
throw new RuntimeException("Only method write(File) is supported.");
}
@Override
public String getString() {
throw new RuntimeException("Only method write(File) is supported.");
}
@Override
public String getFieldName() {
return fieldName;
}
@Override
public void setFieldName(String name) {
this.fieldName = name;
}
@Override
public boolean isFormField() {
return formField;
}
@Override
public void setFormField(boolean state) {
this.formField = state;
}
@Override
public OutputStream getOutputStream() throws IOException {
throw new IOException("Only method write(File) is supported.");
}
}