java - 如何在单个构建器类中拥有多个构建器模式？

Question

我有两种类型的有效载荷来自上游:要么是 PayloadA或 PayloadB .
PayloadA包含这么多字段:

createTimestamp
sentTimestamp
schemaId
eventId
producerId
guid
deviceId
langId
sessionId

PayloadB包含这么多字段:

createTimestamp
sentTimestamp
schemaId
eventId
producerId
eventType
payloadVersion
creationDate
expirationSeconds
payload

所以前 5 个字段在它们之间是通用的。一般来说，他们会有更多的领域。

我想为此创建一个线程安全的构建器模式。所以我应该有一个 Payload构建器模式类，其中包含来自两个有效负载的所有字段？或者我应该有 PayloadA和 PayloadB另一个内部的构建器模式类 Payload builder类和 PayloadA的常用字段和 PayloadB将成为 Payload 的一部分类(class)？

为此类问题制作构建器模式的最佳方法是什么。让我们说 PayloadA builder 模式 deviceId是必填字段。而对于 PayloadB builder 模式 eventType是必填字段。

Answer 1

我建议使用 static nested builder (item 2)模式在这里。

这是你可以做的

创建 abstract类(class)Payload具有共同属性

创建 PayloadA和 PayloadB其中扩展 Payload带有静态嵌套 Builder对于每个。

让线程安全由使用/构造这些对象的方法处理(不需要 Builder 是线程安全的)。

Payload

public abstract class Payload {

    private String createTimestamp;
    private String sentTimestamp;
    private String schemaId;
    private String eventId;
    private String producerId;

    //getters, setters, equals, hashcode, toString, compareTo, etc.
}

PayloadA (PayloadB would be similar)

class PayloadA extends Payload {
    private String guid;
    private String deviceId;
    private String langId;
    private String sessionId;

    private PayloadA() {
        //avoid direct instantiation
    }

    public static class Builder {

        private String guid;
        private String deviceId;
        private String langId;
        private String sessionId;

        public Builder setLangId(String langId) {
            this.langId = langId;
            return this;
        }

        public Builder(String deviceId) {
            //validations
            this.deviceId = deviceId;
        }

        public PayloadA build() {
            //validations
            return new PayloadA();
        }

        //other setters returning this Builder
    }
}

Usage (construct the appropriate Payload from the upstream data

public Payload constructPayload(final Data data) {

    //implement any thread safety mechanism as requirdhere. 
    // synchronized is just for explanatory purposes
    synchronized (data) {
        if (data.getType().equals("PayloadA")) {
            return new PayloadA.Builder(data.getDeviceId())
                    //.setGuid("someGuid")
                    //other setters
                    .build();
        } else {
            return new PayloadB.Builder(data.getEventType())
                    //.setCreationDate("someCreationDate")
                    // other setters
                    .build();
        }
    }
}

希望这可以帮助。