阅读该问题的答案。

所以，在

String button1 = request.getParameter("button1");
String button2 = request.getParameter("button2");

不为null的值是按下的按钮。

或者，如果要为两个按钮使用相同的名称，则可以设置不同的值

<input type="submit" name="act" value="delete"/>
<input type="submit" name="act" value="update"/>

然后

String act = request.getParameter("act");
if (act == null) {
    //no button has been selected
} else if (act.equals("delete")) {
    //delete button was pressed
} else if (act.equals("update")) {
    //update button was pressed
} else {
    //someone has altered the HTML and sent a different value!
}