如何根据特定按钮单击从谷歌应用引擎数据存储中获取特定实体答案

【问题标题】：How to get thespecific entity from google app engine datastore according to the specific button click如何根据特定按钮单击从谷歌应用引擎数据存储中获取特定实体
【发布时间】：2014-01-03 10:53:55
【问题描述】：

我的 Jsp 文件是这样的。它有 2 个按钮。当我点击第一个按钮时，应该选择数据存储中的第一个实体，并且与第二个按钮相同。

 <%@ page language="java" contentType="text/html; charset=ISO-8859-1"
 pageEncoding="ISO-8859-1"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 
 "http://www.w3.org/TR/html4/loose.dtd"> 
 <html>
 <head>
  <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
 <title>Insert title here</title>
 </head>
 <body>
    <body style="background-color:black;">


 <p>
  <p><input type="button" name="first" value="0C F0 0400" style="background-     
 color:#006600; color:#FFFFFF ; height:100px; width:200px"    
 onclick="location.href='hello';"> </p>
<p><input type="button" name="first" value="0D F0 0800" style="background-  
color:#006600; color:#FFFFFF ; height:100px; width:200px" 
 onclick="location.href='hello';">
</p>

</body>
</html>

这是小服务程序。如何在第一个按钮单击时获取第一个实体，在第二个按钮单击时获取第二个实体。

package pack.exp;
import java.io.IOException;
import javax.servlet.http.*;

import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.EntityNotFoundException;
 import com.google.appengine.api.datastore.Key;
import com.google.appengine.api.datastore.KeyFactory;


@SuppressWarnings("serial")
public class HelloServlet extends HttpServlet 
{
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws   
    IOException 
{
    Key k1 = KeyFactory.createKey("Employee","E1");    
    Key k2 = KeyFactory.createKey("Employee","E2");        

    String firstName1 = "Sam";
    String lastName1 = "Well";

    String firstName2 = "John";
    String lastName2 = "Morgan";


    Entity bs1 = new Entity(k1);
    Entity dm1 = new Entity(k2);

    bs1.setProperty("FN", firstName1);     
    bs1.setProperty("LN", lastName1); 

    dm1.setProperty("FN", firstName2);     
    dm1.setProperty("LN", lastName2);

    DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
    datastore.put(bs1);
    datastore.put(dm1);

    Entity bs2 = null;
    Entity dm2 = null;

    try 
    {
        bs2= datastore.get(k1);
        dm2= datastore.get(k2);
    }

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

    String fName1= (String) bs2.getProperty("FN");
    String lName1= (String) bs2.getProperty("LN");

    String fName2= (String) dm2.getProperty("FN");
    String lName2= (String) dm2.getProperty("LN");

    resp.setContentType("text/plain");
    resp.getWriter().println("Person1 Details------> " + fName1 + "  " + lName1);   

    resp.getWriter().println("Person2 Details------> " + fName2 + "  " + lName2);   

}
}

【问题讨论】：

标签： java google-app-engine jsp servlets bigtable

【解决方案1】：

首先，您需要使用 servlet 的 doGet() 方法将值存储到数据存储中。

您可以使用以下代码做到这一点：

public void doGet(HttpServletRequest req, HttpServletResponse resp) throws   
IOException 
{
   Entity employee1=new Entity("Employee","Employee1");  
   Entity employee2=new Entity("Employee","Employee2");
   employee1.setProperty("FN", "Sam");     
   employee1.setProperty("LN", "Sam"); 
   employee2.setProperty("FN", "John");     
   employee2.setProperty("LN", "Morgan");   
  DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
try{
       datastore.put(employee1);
      datastore.put(employee2);
   }
   catch(DatastoreFailureException d){
        d.printStackTrace();
    }
}

然后在 doPost 方法中获取点击按钮的值。 JSP 代码我已经在你的另一个问题中回答了。

public void doPost(HttpServletRequest req, HttpServletResponse resp) throws   
IOException 
{
String key=req.getParameter("good");
Key key = KeyFactory.createKey("Employee", key);
Entity employee=datastore.get(key);
resp.setContentType("text/plain");
resp.getWriter().println("Person Details------> " + employee.getProperty("FN")+ "  " +employee.getProperty("LN"));
}

【讨论】：

你能解释一下 Util.persistEntity(employee1);
请更改。 Util.persistEntity() 到数据存储对象。