java - .setProperty 100% 的时间都不起作用

Question

编辑:代码已更新以包含 @Igor Artamonov 建议的更改， 但问题仍然出现!我确实注意到了以下内容 reference to this image ，所有者 2 有高度值，没有 tool_proficiency 值，直到添加所有者 3，然后 2 的高度值消失，出现 2 的工具值，2 在创建时拥有史密斯工具
编辑结束

这可能类似于“This Question”，但我无法使用那里给出的解决方案解决问题，而且我无法发表评论，因为我的代表太少了:(

所以我希望你不介意我问我在这里的问题:) *注意如果有更好的地方让我提出我的问题或有任何问题请告诉我，我在这里很新:P

我的网页有一个 java 帮助程序，用于设置数据存储中实体的属性，但每次至少会错过一项(如果不是更多的话)？所有项目都使用相同的功能设置!

JSP页面上的代码:

String Username = (String)session.getAttribute("username");
System.out.println("Username carried from session variable = "+Username);

if(request.getParameter("alignment")!=null
&& request.getParameter("Size")!=null 
&& request.getParameter("age")!=null
&& request.getParameter("tools")!=null){

    String HD = "Hill Dwarf";
    String Age = request.getParameter("age");   
    String Alignment = request.getParameter("alignment");   

    int Size = Integer.parseInt(request.getParameter("Size"));
    int Rem = Size%12;
    Size = (Size-(Size%12))/12;
    String Height = (Size+"ft "+Rem+"in");

    String Tools = request.getParameter("tools");   

    System.out.println("setString for hill dwarf: ");
    login.setString(Username, "Race", HD);
    System.out.println("setString for age: ");
    login.setString(Username, "Age", Age);  
    System.out.println("setString for Alignment: ");
    login.setString(Username, "Alignment", Alignment);  
    System.out.println("setString for height: ");
    login.setString(Username, "Height", Height);    
    System.out.println("setString for tools: ");
    login.setString(Username, "Tool_Proficiency", Tools);   
    System.out.println("redirecting to class page");
    response.sendRedirect("class.jsp");
}

登录助手中的代码:

    public void setString(String usernamein,String columnin, String stringin){
    Transaction txn = datastore.beginTransaction();
    try{
        Filter usernamefilter = new FilterPredicate("owner",
        FilterOperator.EQUAL, usernamein);
        Query validuserquery = new Query("Char").setFilter(usernamefilter);
        Entity theUser = datastore.prepare(validuserquery).asSingleEntity();
        System.out.println("Username passed to setString = "+usernamein);
        System.out.println("Column name passed to setString = "+columnin);
        System.out.println("String passed to setString = "+stringin);
        System.out.println("Query = "+validuserquery);
        if (theUser==null && counter < 30){
            System.out.println("theUser was equal to null");
            try {
                System.out.println("sleeping for 400ms");
                Thread.sleep(400);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            counter ++;
            System.out.println("counter increased, counter = "+counter);
            System.out.println("Recursing function");
            setString(usernamein,columnin,stringin);
        }else{
            System.out.println("theUser was not == null ");
            System.out.println("inputting: "+columnin+" = "+stringin);
            theUser.setProperty(columnin,stringin);
            datastore.put(theUser);
            System.out.println("item added");
        }
        txn.commit();
    }finally{
        if (txn.isActive()){
            txn.rollback();
        }
    }
}

如果有人需要我解释代码，我只会问:)

好的，这是将年龄、对齐方式等放入数据存储中的代码，但它在数据存储中给出了这个结果？我一生都不知道为什么!？

这本来是一张图像，但我需要 10 次代表，所以你必须 follow this link for the image :(再次抱歉

这是 eclipse 控制台从所有 System.out.println() 获取的内容 这不是代码，但我会将其放入代码片段中以提高可读性:)

HillDwarf page loaded
Username carried from session variable = 12
setString for hill dwarf: 
Username passed to setString = 12
Column name passed to setString = Race
String passed to setString = Hill Dwarf
Query = SELECT * FROM Char WHERE owner = 12
theUSer was not == null 
inputting: Race = Hill Dwarf
item added
setString for age: 
Username passed to setString = 12
Column name passed to setString = Age
String passed to setString = 10
Query = SELECT * FROM Char WHERE owner = 12
theUSer was not == null 
inputting: Age = 10
item added
setString for Alignment: 
Username passed to setString = 12
Column name passed to setString = Alignment
String passed to setString = N
Query = SELECT * FROM Char WHERE owner = 12
theUSer was not == null 
inputting: Alignment = N
item added
setString for height: 
Username passed to setString = 12
Column name passed to setString = Height
String passed to setString = 4ft 5in
Query = SELECT * FROM Char WHERE owner = 12
theUSer was not == null 
inputting: Height = 4ft 5in
item added
setString for tools: 
Username passed to setString = 12
Column name passed to setString = Tool_Proficiency
String passed to setString = Brewer's Supplies
Query = SELECT * FROM Char WHERE owner = 12
theUSer was not == null 
inputting: Tool_Proficiency = Brewer's Supplies
item added
redirecting to class page

因此，如图所示，我的问题是数据存储区并未每次都获取所有项目，即使我每次都使用相同的帮助器方法!

请帮助我几天来一直在尝试通过多种方法解决这个问题:(

Answer 1

您没有使用事务，因此某些写入会被其他写入替换。

试试这个:

DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
Transaction txn = datastore.beginTransaction();
try {
    /// your current code
    txn.commit();
} finally {
    if (txn.isActive()) {
        txn.rollback();
    }
}

参见https://cloud.google.com/appengine/docs/java/datastore/transactions

PS，您还应该了解，您当前的代码比在一个 .put 中进行相同更新的代码贵 4 倍。我认为没有任何理由要为每个字段分别进行 4 次。