尝试通过Java+sparkSession从Cassandra DB接收JSON数据时出错

Question

我试图通过Java+sparkSession从Cassandra表读取数据，方法应该将其作为JSON返回。

这是我的数据库：

CREATE TABLE user (
  user_id               uuid,
  email                  text, 
  first_name          text,
  last_name          text,
  user_password   text,
  created_date      timestamp, 
  updated_date     timestamp,
  PRIMARY KEY (user_id)
) WITH comment = 'List of all registered and active users';

public String getAccountData(UUID userid) throws ClassNotFoundException, SQLException {
        SparkSession sparkSession = config.getSparkSession();
        //"SELECT user.first_name,user.last_name, user.email FROM chat.user where user.id="+userid+";");

        Account account = new Account();
        Encoder<Account> accountEncoder = Encoders.bean(Account.class);

return sparkSession
        .read()
        .format("org.apache.spark.sql.cassandra")
        .options(new HashMap<String, String>() {
            {
                put("keyspace", "chat");
                put("table", "user");
            }
        })
        .load()
        .select("first_name", "last_name", "email")
        .filter("user_id = '" + userid +"'")
        .toJSON()
        .as(accountEncoder)
        .toString();
    }

package rest.account;

import java.io.Serializable;


public class Account implements Serializable {

   private String user_id;
   private String first_name;
   private String last_name;   
   private String email;

   public Account(){}

   public Account(String user_id, String first_name, String last_name, String email){
      this.user_id = user_id;
      this.first_name = first_name;
      this.last_name = last_name;
      this.email = email;
   }
   //------------------------------
   public String getId() {
      return user_id;
   }

   public void setId(String user_id) {
      this.user_id = user_id;
   }

   //------------------------------
   public String getFirstName() {
      return first_name;
   }

   public void setFirstName(String first_name) {
      this.first_name = first_name;
   }

   //------------------------------
   public String getLastName() {
          return last_name;
       }

   public void setLastName(String lastName) {
   this.last_name = last_name;
   }
   //------------------------------    
   public String getEmail() {
      return email;
   }

   public void setEmail(String email) {
      this.email = email;
   }        
}

HTTP状态500-org.glassfish.jersey.server.ContainerException：org.apache.spark.sql.AnalysisException：无法解析给定的输入列[value]；

类型异常报告

消息org.glassfish.jersey.server.containerexception：org.apache.spark.sql.analysisexception：无法解析给定的输入列[value]；

org.glassfish.jersey.server.containerexception：org.apache.spark.sql.analysisexception：无法解析给定的输入列[value]；responsewriter.rethrow（responsewriter.java:278)org.glassfish.jerse.servlet.internal.responsewriter.failure（responsewriter.java:260)org.glassfish.jerse.server.serverruntime$responder.process（serverruntime.java:509)org.glassfish.jerse.server.serverruntime$2.run（serverruntime.java:334)org.glassfish.jerse.internal.errors$1.callrvice（webcomponent.java:427)org.glassfish.jersey.servlet.servletcontainer.service（servletcontainer.java:388)org.glassfish.jersey.servlet.servletcontainer.service（servletcontainer.java:341)org.glassfish.jersey.servlet.servletcontainer.service（servletcontainer.java:228)org.apache.tomcat.websocket.server.wsfilter.dofilter（

Apache Tomcat/9.0.0.m13

如果我没有这个转换到JSON代码，那么方法返回，例如：

但不是像First Name、Last Name、[e-mail]这样的真实值

我会感激任何帮助的！

Answer 1

在GetAccountData方法中，请尝试下面的代码。

return sparkSession
    .read()
    .format("org.apache.spark.sql.cassandra")
    .options(new HashMap<String, String>() {
        {
            put("keyspace", "chat");
            put("table", "user");
        }
    })
    .load()
    .select("first_name", "last_name", "email")
    .filter("user_id = '" + userid +"'")
    .toJSON()
    .first();
}