java - 如何从另一个类访问用户定义的 List<> 值？

Question

我正在使用 spring-boot 开发一个 API。基本上我想从 Service 类获取 PortedNumber 类的所有值并将它们存储到一个文本文件中。

public class Service {
    PortedNumber portedNumber = new PortedNumber();
    public AcknowledgeMessage checkRequestValidity(Request request) throws IOException {
        AcknowledgeMessage acknowledgeMessage=new AcknowledgeMessage();
        long msisdn = portedNumber.getNumber();
        String recipientRC = portedNumber.getRecipientRC();
        String donorRC = portedNumber.getDonorRC();
        String nrhRC = portedNumber.getNrhRC();
        
        try(FileWriter fw = new FileWriter("myfile.txt", true);
                BufferedWriter bw = new BufferedWriter(fw);
                PrintWriter out = new PrintWriter(bw))
            {
                out.println(msisdn+"\t"+recipientRC+"\t"+donorRC+"\t"+nrhRC);   
            } catch (IOException e) {
                //exception handling left as an exercise for the reader
            }

        return acknowledgeMessage;
    }
}

public class Request {

    protected List<PortedNumber> singleNumber;

    public List<PortedNumber> getSingleNumber() {
        if (singleNumber == null) {
            singleNumber = new ArrayList<PortedNumber>();
        }
        return this.singleNumber;
    }
}



public class PortedNumber {

    protected long number;
    @XmlElement(required = true)
    protected String recipientRC;
    @XmlElement(required = true)
    protected String donorRC;
    @XmlElement(required = true)
    protected String nrhRC;
    @XmlElement(required = true)
    protected PortedAction portedAction;
    protected List<ExtensionElement> extension;

    public long getNumber() {
        return number;
    }

    public void setNumber(long value) {
        this.number = value;
    }

    public String getRecipientRC() {
        return recipientRC;
    }

    public void setRecipientRC(String value) {
        this.recipientRC = value;
    }

    public String getDonorRC() {
        return donorRC;
    }
   

    public void setDonorRC(String value) {
        this.donorRC = value;
    }

    public String getNrhRC() {
        return nrhRC;
    }

    public void setNrhRC(String value) {
        this.nrhRC = value;
    }

    public PortedAction getPortedAction() {
        return portedAction;
    }

    public void setPortedAction(PortedAction value) {
        this.portedAction = value;
    } 
}

如何从 Service 类中获取 PortedNumber 的 getNumber() 的值？

我试过 long number = portedNumber.getNumber(); 但是，它不起作用。它为 msisdn 存储 0，为其他存储 null。

我无法获取 Arraylist 值。我想获取 Arraylist 的所有值并将其存储到文本文件中。

Answer 1

您使用 PortedNumber portedNumber = new PortedNumber(); 在您的 Service 中实例化 portedNumber 属性。这意味着它没有初始化的属性，并且所有属性都将具有它们的默认值(对象为 null，long 为 0)。

您永远不会设置这些属性，因此预计 It stores 0 for msisdn and null for others. 如您所写。

---

如果我正确理解了您的问题，您希望遍历 request 中的 PortedNumber 列表并将它们写入文件。如果是这种情况，请尝试以下操作:

public class Service {

    public AcknowledgeMessage checkRequestValidity(NPCHRequest request) throws IOException {
        AcknowledgeMessage acknowledgeMessage=new AcknowledgeMessage();
        
        try(FileWriter fw = new FileWriter("myfile.txt", true);
                BufferedWriter bw = new BufferedWriter(fw);
                PrintWriter out = new PrintWriter(bw)) {
                for (PortedNumber portedNumber : request.getSingleNumber()) {
                    long msisdn = portedNumber.getNumber();
                    String recipientRC = portedNumber.getRecipientRC();
                    String donorRC = portedNumber.getDonorRC();
                    String nrhRC = portedNumber.getNrhRC();
                    out.println(msisdn+"\t"+recipientRC+"\t"+donorRC+"\t"+nrhRC); 
                }  
            } catch (IOException e) {
                //exception handling left as an exercise for the reader
            }

        return acknowledgeMessage;
    }
}