//设置输出类容的类型，按照下面设置后flush()才会起作用

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();

/***

不设置ContentType直接使用flush()不会有作用。

如果要flush()起作用，必须先向缓冲区填充一定的内容（测试为1024个字符）。
网上看到的原因是容器认为缓冲区的内容过少发送的效率不高。


设置了ContentType为text/html后，flush()就会立即起作用。
可能是因为动态生成Html的时候加载数据比较耗时，可以先返回后让浏览器解析样式。（个人猜想）

上面的内容没有在任何的官方文档中看到。唯一在官方文档中看到和内容大小有关系的是关于Buffer大小的设置：

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()

***/