lombok - 多个镜头中的@Builder模式

Question

我用@Builder的龙目岛的项目,所以我认为有这样的例子:

@Builder
public class Client {

    private @Getter @Setter Integer id;
    private @Getter @Setter String name;

}

这相当于:

public class Client {

    private @Getter @Setter Integer id;
    private @Getter @Setter String name;

    public static class Builder {

        private Integer id;
        private String name;

        private Builder() {
        }

        public Builder id(final Integer value) {
            this.id = value;
            return this;
        }

        public Builder name(final String value) {
            this.name = value;
            return this;
        }

        public Client build() {
            return new Client(this);
        }
    }

    public static Client.Builder builder() {
        return new Client.Builder();
    }

    private Client(final Builder builder) {
        this.id = builder.id;
        this.name = builder.name;
    }
}

当我尝试一次性设置所有字段时没有问题:

public static void main(String[] args) {
    Client client = Client.builder()
            .id(123)
            .name("name")
            .build();
}

输出:

Client{id=123, name=name}

现在,考虑我想要多次拍摄.例如:

public static void main(String[] args) {
    Client client = Client.builder()
            .id(123)//<-------------------------- Set just the id
            .build();

    client = Client.builder()
            .name("name")//<--------------------- Set name
            .build();

}

这在逻辑上返回null为id:

Client{id=null, name=name}

通常,没有lombok,我通过在Builder类中添加一个采用相同对象的新构造函数来解决此问题:

public static class Builder {
    // ...
    public Builder(Client client) {
        this.id = client.id;
        this.name = client.name;
    }
    // ...
}

然后我将我的对象传递给该构造函数:

Client client = Client.builder()
        .id(123)
        .build();

client = new Client.Builder(client)//<---------------- Like this 
        .name("name")
        .build();

这解决了我的问题,但我不能用lombok来解决它.有什么方法可以解决这个问题吗？

Answer 1

根据您的使用情况,您还可以保留对现有构建器的引用.你可以有多个build方法.

披露:我是一名lombok开发者.

Answer 2

您可以使用该toBuilder属性来执行此操作.

@Builder(toBuilder=true)
public class Client {
    private @Getter @Setter Integer id;
    private @Getter @Setter String name;
}

然后你可以这样使用它

public void main(String[] args){
    Client client = Client.builder()
        .id(123)
        .build();

    client = client.toBuilder()
        .name("name")
        .build();
}