; lineNumber: 1; columnNumber: 1; Content is not allowed in prolog

用sax读xml文件时常会出现这个异常，一般上网可以看到的原因是:

   在java中测试inputstream中是否有bom可以用apache commons IO 的，如果你的项目有引入IO的情况下

   BOM的基础知识可以参考:/faq/utf_bom.html

   也贴一个过滤BOM的小方法

private static InputStream checkForUtf8BOMAndDiscardIfAny(InputStream inputStream) throws IOException {
    PushbackInputStream pushbackInputStream = new PushbackInputStream(new BufferedInputStream(inputStream), 3);
    byte[] bom = new byte[3];
    if ((bom) != -1) {
        if (!(bom[0] == (byte) 0xEF && bom[1] == (byte) 0xBB && bom[2] == (byte) 0xBF)) {
            (bom);
        }
    }
    return pushbackInputStream; 
}

2.非良构的xml内容,例如在<?xml前出现非法的字符

   可以采用正则从<?xml开始截取内容

3.今天我发现的是因为:Accept-Encoding启用了压缩传输,可以试着把Accept-Encoding设成:identity,同时也要注意是否采用Chunked Transfer Encoding(分段传输)

后话,有人说直接把流传给sax parser可以过滤掉。当然我用的sax,jaxp发现不会过滤掉。文档测试的环境:java 7 + xerces sax。全部异常栈

; lineNumber: 1; columnNumber: 1; Content is not allowed in prolog.
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