Question

/**
 * ConnectDB2.java , i'm fetching data from database and setting values to model class.
 */
  package org.com.repair.spotify.repair.db;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.ws.rs.Path;

import org.com.repair.spotify.repair.model.RepairDetails;

/**
 * @author www.javaworkspace.com
 * 
 */
@Path("/connectDB2")
public class ConnectDB2 {
    Connection connection = null;
    ResultSet resultSet = null;
    Statement statement = null;
    String deviceName;
    String deviceModel;
    String ticketId;
    String issue;
    String deviceType;

    public ConnectDB2() {
        try {

            Class.forName("com.ibm.db2.jcc.DB2Driver");
            connection = DriverManager.getConnection(
                    "jdbc:db2://localhost:50000/HELLO", "db2admin", "admin");
            statement = connection.createStatement();

            resultSet = statement.executeQuery("SELECT * FROM DEVICE ");
            while (resultSet.next()) {
                System.out.println("DEVICE BRAND:" + resultSet.getString(1)
                        + " || ISSUE: " + resultSet.getString(2) + " ||MODEL:"
                        + resultSet.getString(3) + "||TYPE:"
                        + resultSet.getString(4));
                RepairDetails Rd = new RepairDetails();
                Rd.setDeviceModel(resultSet.getString(1));
                Rd.setIssue(resultSet.getString(2));
                Rd.setDeviceType(resultSet.getString(3));
                Rd.setDeviceType(resultSet.getString(4));

            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                resultSet.close();
                statement.close();
                connection.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

    }

}

/ RepairDetails.java ==＆GT;我的Model类 /

package org.com.repair.spotify.repair.model;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class RepairDetails {

    String deviceName;
    String deviceModel;
    String ticketId;
    String issue;
    String deviceType;

    public RepairDetails() {

    }

    public RepairDetails(String deviceName, String deviceModel,
            String ticketId, String issue, String deviceType) {
        super();
        this.deviceName = deviceName;
        this.deviceModel = deviceModel;
        this.ticketId = ticketId;
        this.issue = issue;
        this.deviceType = deviceType;
    }

    public String getDeviceName() {
        System.out.println("getter" + deviceName);
        return deviceName;
    }

    public void setDeviceName(String deviceName) {
        System.out.println("setter" + deviceName);
        this.deviceName = deviceName;
    }

    public String getDeviceModel() {
        return deviceModel;
    }

    public void setDeviceModel(String deviceModel) {
        System.out.println("setter" + deviceModel);
        this.deviceModel = deviceModel;
    }

    public String getTicketId() {
        return ticketId;
    }

    public void setTicketId(String ticketId) {
        this.ticketId = ticketId;
    }

    public String getIssue() {
        return issue;
    }

    public void setIssue(String issue) {
        System.out.println("setter" + issue);
        this.issue = issue;
    }

    public String getDeviceType() {
        return deviceType;
    }

    public void setDeviceType(String deviceType) {
        System.out.println("setter" + deviceType);
        this.deviceType = deviceType;
    }

}

//我正在尝试从模型中获取值的服务类，但是我提取的是null值，这将进一步传递给getRepairdetails（）

package org.com.repair.spotify.repair.service;
import java.util.ArrayList;
import java.util.List;

import org.com.repair.spotify.repair.db.ConnectDB2;
import org.com.repair.spotify.repair.model.*;

public class RepairService {

    public RepairService() {
        ConnectDB2 db = new ConnectDB2();
    }

    public List<RepairDetails> getRepairService()

    {
        System.out.println("getRepairDetails-->2");
        RepairDetails Rd = new RepairDetails();

        System.out.println("hey im firing");
        RepairDetails RD1 = new RepairDetails(Rd.getDeviceName(),
                Rd.getDeviceModel(), Rd.getIssue(), Rd.getDeviceType(),
                "Mobile");
        List<RepairDetails> list = new ArrayList<RepairDetails>();
        list.add(RD1);
        return list;

    }

}

请帮助我为什么getter返回null值？

Answer 1

让我们从检查RepairDetails类开始。这个实现了一个 POJO （普通的旧Java对象）并包含两个构造函数。

public RepairDetails()
public RepairDetails(String, String, String, String, String)

因此，当您使用第一个构造函数创建对象时，这意味着您没有对字段进行任何设置，这意味着值已初始化为null。

现在让我们来看看RepairService课程。你在getRepairService()方法中有这个代码。

RepairDetails Rd = new RepairDetails();

RepairDetails RD1 = new RepairDetails(Rd.getDeviceName(),
        Rd.getDeviceModel(), Rd.getIssue(), Rd.getDeviceType(),
        "Mobile");

List<RepairDetails> list = new ArrayList<RepairDetails>();
list.add(RD1);

这里我们有以下观察：

Rd是使用第一个构造函数创建的对象，因此Rd中的值有效null。
您正在构建RD1，其值来自Rd，这意味着它们也会null。

我希望你现在能得到它。

尝试从模型类

1 个答案: