java-MongoDB存入文件时奇怪的异常

#pre

     本来把打算文件直接放到服务器上，不过好像直接把文件塞进mongodb更好一些

就打算试一试，老样子百度关键字，看了一些博客之后(= =是不是应该先看官方API)

整理成一段了会报错的代码←_←

public static void test() throws IOException {
    File fin=new File("D:/视听资源/音乐/rm/ruki.mp3");
    MongoClient mc=new MongoClient();
    DB db=new DB(mc,"test");
    GridFS gridFS=new GridFS(db);
    GridFSInputFile gridFSInputFile =gridFS.createFile(fin);
    gridFSInputFile.save();
}

#报错

Exception in thread "main" com.mongodb.MongoException: couldn't save chunks
at com.mongodb.gridfs.GridFSInputFile.save(GridFSInputFile.java:180)
at com.mongodb.gridfs.GridFSInputFile.save(GridFSInputFile.java:160)
at com.listentome.DB.Operations.test.test(test.java:30)
at com.listentome.DB.Operations.test.main(test.java:21)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: java.io.IOException: Stream Closed
at java.io.FileInputStream.readBytes(Native Method)
at java.io.FileInputStream.read(FileInputStream.java:272)
at com.mongodb.gridfs.GridFSInputFile._readStream2Buffer(GridFSInputFile.java:307)
at com.mongodb.gridfs.GridFSInputFile.saveChunks(GridFSInputFile.java:228)
at com.mongodb.gridfs.GridFSInputFile.save(GridFSInputFile.java:178)
... 8 more

看错误日志发现是在调用save函数的时候文件流关闭了

然后就着这个错误搜啊搜没找着符合这个情况的解释←_←

#然后为什么会发生Stream Closed此等奇怪的错误

     不小心发现了gridFS.createFile这个方法重载了好几个，然后就把上边那一行改成了

GridFSInputFile gridFSInputFile =gridFS.createFile(new FileInputStream(fin));
然后好了←_←，为什么会这样，传入File和传入InputStream应该一样吧

#点进源码看了看

public GridFSInputFile createFile(File file) throws IOException {
    FileInputStream fileInputStream = new FileInputStream(file);

    GridFSInputFile var3;
    try {
        var3 = this.createFile(fileInputStream, file.getName(), true);
    } finally {
        fileInputStream.close();  //←_←就是这里，它自己给关了所以save的时候报错了！    }

    return var3;
}

public GridFSInputFile createFile(InputStream in) {
    return this.createFile(in, (String)null);
}