更改不可变的构建器构造函数以使用泛型

Question

我有一个下面的类，它是子类的基本DTO。我需要修复受保护的构造函数，因为Intellij说：“参数化类生成器的原始使用”。有人可以看看，并指出如何重新编写这个构造函数，以支持通用风格在这里。

import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonPOJOBuilder;

import java.util.List;
import java.util.Objects;

import static com.fasterxml.jackson.annotation.JsonProperty.Access.READ_ONLY;

@JsonDeserialize(builder = PageableResponse.Builder.class)
public class PageableResponse<T>
{
    @JsonProperty(value = "data", required = true, access = READ_ONLY)
    private final List<T> data;
    @JsonProperty(value = "total", required = true, access = READ_ONLY)
    private final Long total;

    // constructor required for spring
    public PageableResponse(List<T> data, Long total)
    {
        this.data = data;
        this.total = total;
    }

    // here is an issue: Raw use of parameterized class Builder
    protected PageableResponse(Builder builder)
    {
        data = (List<T>) builder.data; // and here unchecked cast as well
        total = builder.total;
    }

    public static <T extends Builder<T>> Builder<T> newBuilder()
    {
        return new Builder<T>();
    }

    public static <T extends Builder<T>> Builder<T> newBuilder(PageableResponse<T> copy)
    {
        Builder<T> builder = new Builder<T>();
        builder.data = copy.getData();
        builder.total = copy.getTotal();
        return builder;
    }

    public List<T> getData()
    {
        return data;
    }

    public Long getTotal()
    {
        return total;
    }

    @Override
    public boolean equals(Object o)
    {
        if (this == o)
        {
            return true;
        }
        if (o == null || getClass() != o.getClass())
        {
            return false;
        }
        PageableResponse<?> that = (PageableResponse<?>) o;
        return Objects.equals(data, that.data) && Objects.equals(total, that.total);
    }

    @Override
    public int hashCode()
    {
        return Objects.hash(data, total);
    }

    @JsonPOJOBuilder(withPrefix = "")
    public static class Builder<T extends Builder<T>>
    {
        private List<T> data;
        private Long total;

        protected Builder()
        {
        }

        public Builder<T> data(List<T> data)
        {
            this.data = data;
            return this;
        }

        public Builder<T> total(Long total)
        {
            this.total = total;
            return this;
        }

        public PageableResponse<T> build()
        {
            return new PageableResponse<T>(this);
        }
    }
}

你觉得可能吗？有人看到此代码的潜在问题吗？感谢先进。

Answer 1

您可以通过向PageResponse（Builder）构造函数添加类型参数来修复警告。

protected PageableResponse(Builder<T> builder)

此外，您的Builder的类型参数定义有点奇怪。

public static class Builder<T extends Builder<T>>

暗示T必须是Builder。

public static class Builder<T>

意味着T可以是任何东西。可能更有意义？