java - JasperReport 大小限制

Question

有没有办法对 JasperReport 的大小设置限制？我们刚刚查看了一个 WebSphere 6.1 Heapdump，有人试图创建一个报告，结果堆中有 1.5GB 的内存。它使我们的 Websphere 服务器瘫痪。
谢谢，
吨

Answer 1

我不熟悉 JasperReports，但您可以 wrap your I/O streams以确保读取/写入的数据量不超过定义的限制。

OutputStream例子:

public class LimitedSizeOutputStream extends OutputStream {

    private final OutputStream delegate;
    private final long limit;
    private long written = 0L;

    /**
     * Creates a stream wrapper that will throw an IOException if the write
     * limit is exceeded.
     * 
     * @param delegate
     *            the underlying stream
     * @param limit
     *            the maximum number of bytes this stream will accept
     */
    public LimitedSizeOutputStream(OutputStream delegate, long limit) {
        this.delegate = delegate;
        this.limit = limit;
    }

    private void checkLimit(long byteCount) throws IOException {
        if (byteCount + written > limit) {
            throw new IOException("Exceeded stream size limit");
        }
        written += byteCount;
    }

    @Override
    public void write(int b) throws IOException {
        checkLimit(1);
        delegate.write(b);
    }

    @Override
    public void write(byte[] b) throws IOException {
        checkLimit(b.length);
        delegate.write(b);
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        checkLimit(len);
        delegate.write(b, off, len);
    }

    @Override
    public void close() throws IOException {
        delegate.close();
    }

}

包装 InputStream 也很容易.