我使用lombok project的@Builder,所以請(qǐng)考慮我有這個(gè)例子：

@Builder
public class Client {

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

}

這相當(dāng)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;
    }
}

當(dāng)我嘗試一次性設(shè)置所有字段時(shí)沒(méi)有問(wèn)題：

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

輸出：

Client{id=123, name=name}

現(xiàn)在,考慮我想要多次拍攝.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();

}

這在邏輯上為id返回null：

Client{id=null, name=name}

通常,沒(méi)有l(wèi)ombok,我通過(guò)在Builder類(lèi)中添加一個(gè)新的構(gòu)造函數(shù)來(lái)解決這個(gè)問(wèn)題,該構(gòu)造函數(shù)采用相同的對(duì)象：

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

然后我將我的對(duì)象傳遞給該構(gòu)造函數(shù)：

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

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

這解決了我的問(wèn)題,但我不能用lombok來(lái)解決它.有什么方法可以解決這個(gè)問(wèn)題嗎？

解決方法:

您可以使用toBuilder屬性來(lái)執(zhí)行此操作.

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

然后你可以這樣使用它

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

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