用java实现multipart/form-data接受请求接口

下面是一个使用Java实现multipart/form-data接受请求的示例代码：

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.URI;
import java.util.List;

import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;

public class MultiPartFormHandler implements HttpHandler {

    public static void main(String[] args) throws Exception {
        HttpServer server = HttpServer.create(new InetSocketAddress(8000), 0);
        server.createContext("/upload", new MultiPartFormHandler());
        server.start();
        System.out.println("Server started on port 8000");
    }

    @Override
    public void handle(HttpExchange exchange) throws IOException {
        String contentType = exchange.getRequestHeaders().getFirst("Content-Type");
        if (contentType != null && contentType.startsWith("multipart/form-data")) {
            InputStream in = exchange.getRequestBody();
            MultiPartFormData formData = new MultiPartFormData(in, contentType);
            List<FormPart> parts = formData.getParts();
            for (FormPart part : parts) {
                if (part.isFile()) {
                    saveFile(part);
                    System.out.println("File saved: " + part.getFileName());
                } else {
                    System.out.println(part.getName() + ": " + part.getText());
                }
            }
        }
        exchange.sendResponseHeaders(200, 0);
        exchange.close();
    }

    private void saveFile(FormPart part) throws IOException {
        File file = new File(part.getFileName());
        OutputStream out = new FileOutputStream(file);
        InputStream in = part.getInputStream();
        byte[] buffer = new byte[1024];
        int read;
        while ((read = in.read(buffer)) != -1) {
            out.write(buffer, 0, read);
        }
        out.close();
        in.close();
    }

}

class MultiPartFormData {

    private List<FormPart> parts;

    public MultiPartFormData(InputStream in, String contentType) throws IOException {
        String boundary = extractBoundary(contentType);
        MultipartStream multipartStream = new MultipartStream(in, boundary.getBytes());
        boolean nextPart = multipartStream.skipPreamble();
        while (nextPart) {
            String header = multipartStream.readHeaders();
            FormPart part = new FormPart(header, multipartStream);
            parts.add(part);
            nextPart = multipartStream.readBoundary();
        }
    }

    private String extractBoundary(String contentType) {
        String[] elements = contentType.split(";");
        for (String element : elements) {
            element = element.trim();
            if (element.startsWith("boundary=")) {
                return element.substring("boundary=".length());
            }
        }
        return null;
    }

    public List<FormPart> getParts() {
        return parts;
    }
}

class FormPart {

    private String name;
    private String fileName;
    private boolean file;
    private String text;
    private InputStream inputStream;

    public FormPart(String header, InputStream inputStream) throws IOException {
        String[] elements = header.split(";");
        for (String element : elements) {
            element = element.trim();
            if (element.startsWith("name=")) {
                name = element.substring("name=".length());
            } else if (element.startsWith("filename=")) {
                fileName = element.substring("filename=".length());
                file = true;
            }
        }
        if (file) {
            this.inputStream = inputStream;
        } else {
            byte[] buffer = new byte[1024];
            int read = inputStream.read(buffer);
            text = new String(buffer, 0, read);
        }
    }

    public String getName() {
        return name;
    }

    public String getFileName() {
        return fileName;
    }

    public boolean isFile() {
        return file;
    }

    public String getText() {
        return text;
    }

    public InputStream getInputStream() {
        return inputStream;
    }

}

该示例使用了Java内置的HttpServer和MultipartStream类来处理multipart/form-data请求。HttpServer是一个简单的HTTP服务器，MultipartStream是处理multipart/form-data请求的类。在handle方法中，我们首先检查请求的Content-Type是否是multipart/form-data类型。如果是，我们使用MultipartStream类来解析请求并获取各个部分的内容。对于每个部分，我们检查它是文件还是文本，并执行相应的操作。在这个示例中，我们只是打印文本内容或保存文件。

注意：该示例代码需要Java 8或更高版本才能运行。