//設置輸出類容的類型，按照下面設置后flush()才會起作用

response.setContentType("text/html; charset=UTF-8");

request.setCharacterEncoding("UTF-8");

PrintWriter writer = response.getWriter();

for(int index = 0 ;index < 5 ;index++){

writer.write("你好！<br />");

writer.flush();

try {

Thread.sleep(1000);

} catch (InterruptedException e) { }

}

writer.close();

/***

不設置ContentType直接使用flush()不會有作用。

如果要flush()起作用，必須先向緩沖區填充一定的內容（測試為1024個字符）。
網上看到的原因是容器認為緩沖區的內容過少發送的效率不高。


設置了ContentType為text/html后，flush()就會立即起作用。
可能是因為動態生成Html的時候加載數據比較耗時，可以先返回后讓瀏覽器解析樣式。（個人猜想）

上面的內容沒有在任何的官方文檔中看到。唯一在官方文檔中看到和內容大小有關系的是關于Buffer大小的設置：

setBufferSize

public void setBufferSize(int size)

Sets the preferred buffer size for the body of the response. The servlet container will use a buffer at least as large as the size requested. The actual buffer size used can be found using getBufferSize.

A larger buffer allows more content to be written before anything is actually sent, thus providing the servlet with more time to set appropriate status codes and headers. A smaller buffer decreases server memory load and allows the client to start receiving data more quickly.

This method must be called before any response body content is written; if content has been written or the response object has been committed, this method throws an IllegalStateException.

 

Parameters:

size - the preferred buffer size

Throws:

java.lang.IllegalStateException - if this method is called after content has been written

See Also:

getBufferSize(), flushBuffer(), isCommitted(), reset()

***/