java - post方法调用一个java类初始化每个请求

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How do servlets work? Instantiation, sessions, shared variables and multithreading
                                
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我使用jsp和servlet创建了一个小型Web应用程序。我的ajax post方法每三秒钟调用一次Java类。我想每隔3秒就知道java类变量isBootRunning，istest1Running，istest1Running是否初始化为“ null”。
如果将针对每个请求进行初始化，则如何防止这种初始化。

我的JSP：

setInterval(function(){
            TestReport();
        }, 3000);
function TestReport(){
var tbname = $("#tbname").attr('class');
var userName = $("#userName").attr('class');
var name = tbname;
var url ="TestReport";
var params = {
        tbname: tbname,
        userName:userName
};
$.post('TestReport', {
    tbname: tbname,
    userName:userName,
}, function(responseText) {
    alert(responseText);
});
}

我的Servlet：

public class TestReport extends HttpServlet {
private static final long serialVersionUID = 1L;
String isBootRunning = null;
String istest1Running = null;
String istest2Running = null;
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {

        File f1 = new File("myfirstpath");//this directory is visible for 10 mins only
        File f2 = new File("mythirdpath");//this directory is visible for 10 mins only
        File f3 = new File("mythirdpath");//this directory is visible for 10 mins only

        if (f1.exists() && f1.isDirectory()) {
            isBootRunning = "Running";
            istest1Running = "Scheduled";
            istest2Running = "Scheduled";
        } else if(f2.exists() && f2.isDirectory()){
            istest1Running = "Running";
            istest2Running = "Scheduled";
            if(isBootRunning=="Running"){
                //here my logic
            }
        } else if(f2.exists() && f2.isDirectory()){

            istest2Running = "Running";
            if(isBootRunning=="Running"){
                //here my logic
            }
            if(istest1Running=="Running"){
                //here my logic
            }
        }
    }
}

最佳答案

之所以面临此问题，是因为每次向Servlet发出新的Ajax请求时，都不会存储/保存先前请求的结果。
可以使用HttpSession解决此问题。您必须在会话对象中保存并获取字符串对象isBootRunning，istest1Running，istest2Running，如下所示：

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    try{
        HttpSession session =null;
        if(request.getSession().isNew()){
             session= request.getSession();//new session
        }else{
             session= request.getSession(false);//current session
        }
        if(null != session && null != session.getAttribute("isBootRunning") && null != session.getAttribute("istest1Running")  && null != session.getAttribute("istest2Running")){
            yourLogic(session);//compute your logic for not null values
        }
        else{
            session.setAttribute("isBootRunning", "");
            session.setAttribute("istest1Running", "");
            session.setAttribute("istest2Running", "");

            yourLogic(session);//compute your logic for null values
        }

    }catch(Exception e){
        e.printStackTrace();
    }
}

private void yourLogic(HttpSession session) {
    File f1 = new File("myfirstpath");//this directory is visible for 10 mins only
    File f2 = new File("mythirdpath");//this directory is visible for 10 mins only
    File f3 = new File("mythirdpath");//this directory is visible for 10 mins only

    String isBootRunning = (String)session.getAttribute("isBootRunning");
    String istest1Running = (String)session.getAttribute("istest1Running");;
    String istest2Running = (String)session.getAttribute("istest2Running");;
    if (f1.exists() && f1.isDirectory()) {
        session.setAttribute("isBootRunning", "Running");
        session.setAttribute("istest1Running", "Scheduled");
        session.setAttribute("istest2Running", "Scheduled");
    } else if(f2.exists() && f2.isDirectory()){
        session.setAttribute("istest1Running", "Scheduled");
        session.setAttribute("istest2Running", "Scheduled");
        if(isBootRunning=="Running"){
            //here my logic
        }
    } else if(f2.exists() && f2.isDirectory()){
        session.setAttribute("istest2Running", "Scheduled");
        istest2Running = "Running";
        if(isBootRunning=="Running"){
            //here my logic
        }
        if(istest1Running=="Running"){
            //here my logic
        }
    }
}

在这里，您的String对象存储在会话对象中。使用会话非常安全，因为会话管理是在您的Web容器中完成的，并且绝不会破坏用户的完整性。
这将防止为以后的请求初始化对象。

关于java - post方法调用一个java类初始化每个请求，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/39786941/