com.offerready.xslt.destination.StreamingHttpResponseDocumentGenerationDestination Maven / Gradle / Ivy

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Utility classes for XSLT processing used at Offer-Ready GmbH

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package com.offerready.xslt.destination;

import lombok.SneakyThrows;

import javax.annotation.CheckForNull;
import javax.annotation.Nonnull;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Streams the result of a transformation directly to an {@link HttpServletResponse}.
 */
public class StreamingHttpResponseDocumentGenerationDestination implements DocumentGenerationDestination {
    
    protected @Nonnull HttpServletResponse response;
    protected boolean outputStarted = false; // Java silently ignores setting headers after content started, we make it non-silent
    
    public StreamingHttpResponseDocumentGenerationDestination(@Nonnull HttpServletResponse response) {
        this.response = response;
    }

    @Override public void setContentType(@Nonnull String contentType) {
        if (outputStarted) throw new IllegalStateException("Cannot set headers after content started");
        response.setContentType(contentType);
    }
    
    @Override public void setContentDispositionToDownload(@CheckForNull String filename) {
        if (outputStarted) throw new IllegalStateException("Cannot set headers after content started");
        if (filename == null) {
            response.setHeader("content-disposition", "attachment");
        } else {
            if ( ! filename.matches("[\\w.\\-]+")) throw new RuntimeException("Filename '" + filename + "' invalid");
            response.setHeader("content-disposition", "attachment; filename=\"" + filename + "\"");
        }
    }

    @SneakyThrows(IOException.class)
    @Override public @Nonnull OutputStream getOutputStream() {
        outputStarted = true;
        return response.getOutputStream();
    }
}