java - JasperReport 大小限制

Question

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

Answer 1

我不熟悉 JasperReports，但您可以包装您的 I/O 流以确保读取/写入的数据量不超过定义的限制。

输出流示例：

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。

Answer 2

JasperReports 现在具有限制报告输出大小的“报告管理器”。例如，您可以设置这些配置参数：

net.sf.jasperreports.governor.max.pages.enabled=[true|false]

net.sf.jasperreports.governor.max.pages=[integer]

有关更多信息，请参阅JasperReports 论坛上的此帖子。

Answer 3

您是否尝试过限制从数据库返回的记录集中的行？