android 中的MultipartEntity 类

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Random;

import org.apache.commons.httpclient.methods.multipart.Part;
import org.apache.http.Header;
import org.apache.http.entity.AbstractHttpEntity;
import org.apache.http.message.BasicHeader;
import org.apache.http.params.HttpParams;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EncodingUtils;

public class MultipartEntity extends AbstractHttpEntity {
private static final String MULTIPART_FORM_CONTENT_TYPE = "multipart/form-data";

public static final String MULTIPART_BOUNDARY = "http.method.multipart.boundary";

private static byte[] MULTIPART_CHARS = EncodingUtils
.getAsciiBytes("-_1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");

private static byte[] generateMultipartBoundary() {
Random rand = new Random();
byte[] bytes = new byte[rand.nextInt(11) + 30]; // a random size from 30
// to 40
for (int i = 0; i < bytes.length; i++) {
bytes[i] = MULTIPART_CHARS[rand.nextInt(MULTIPART_CHARS.length)];
}
return bytes;
}

protected Part[] parts;

private byte[] multipartBoundary;

private HttpParams params;

private boolean contentConsumed = false;

public MultipartEntity(Part[] parts, HttpParams params) {
if (parts == null) {
throw new IllegalArgumentException("parts cannot be null");
}
if (params == null) {
throw new IllegalArgumentException("params cannot be null");
}
this.parts = parts;
this.params = params;
}

public MultipartEntity(Part[] parts) {
setContentType(MULTIPART_FORM_CONTENT_TYPE);
if (parts == null) {
throw new IllegalArgumentException("parts cannot be null");
}
this.parts = parts;
this.params = null;
}

protected byte[] getMultipartBoundary() {
if (multipartBoundary == null) {
String temp = null;
if (params != null) {
temp = (String) params.getParameter(MULTIPART_BOUNDARY);
}
if (temp != null) {
multipartBoundary = EncodingUtils.getAsciiBytes(temp);
} else {
multipartBoundary = generateMultipartBoundary();
}
}
return multipartBoundary;
}

public boolean isRepeatable() {
for (int i = 0; i < parts.length; i++) {
if (!parts[i].isRepeatable()) {
return false;
}
}
return true;
}

public void writeTo(OutputStream out) throws IOException {
Part.sendParts(out, parts, getMultipartBoundary());
}

public Header getContentType() {
StringBuffer buffer = new StringBuffer(MULTIPART_FORM_CONTENT_TYPE);
buffer.append("; boundary=");
buffer.append(EncodingUtils.getAsciiString(getMultipartBoundary()));
return new BasicHeader(HTTP.CONTENT_TYPE, buffer.toString());
}

public long getContentLength() {
try {
return Part.getLengthOfParts(parts, getMultipartBoundary());
} catch (Exception e) {
return 0;
}
}

public InputStream getContent() throws IOException, IllegalStateException {
if (!isRepeatable() && this.contentConsumed) {
throw new IllegalStateException("Content has been consumed");
}
this.contentConsumed = true;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
Part.sendParts(baos, this.parts, this.multipartBoundary);
ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
return bais;
}

public boolean isStreaming() {
return false;
}
}