Java改进特定类的Builder模式 [英] Java improving Builder pattern on a specific class

问题描述

目前我有这个实现Builder模式的类，为了便于阅读，我选择省略一些方法，更确切地说我只显示用户名的构建方法 。

currently I have got this class which implements the Builder pattern, for sake of readibility I have chosen to omit some methods, more precisely I only show the build methods of username.

package dao.constraint;

import java.util.Arrays;

public class AccountConstraint {
    private Constraint<Range<Integer>> accountIdConstraint;
    private Constraint<String> usernameConstraint;
    private Constraint<String> passwordConstraint;
    private Constraint<String> emailConstraint;

    private AccountConstraint(Builder builder) {
        this.accountIdConstraint = builder.accountIdConstraint;
        this.usernameConstraint = builder.usernameConstraint;
        this.passwordConstraint = builder.passwordConstraint;
        this.emailConstraint = builder.emailConstraint;
    }

    public Constraint<Range<Integer>> getAccountIdConstraint() {
        return accountIdConstraint;
    }

    public Constraint<String> getUsernameConstraint() {
        return usernameConstraint;
    }

    public Constraint<String> getPasswordConstraint() {
        return passwordConstraint;
    }

    public Constraint<String> getEmailConstraint() {
        return emailConstraint;
    }

    public Constraint[] getConstraints() {
        return Arrays.asList(this.getAccountIdConstraint(), this.getUsernameConstraint(), this.getPasswordConstraint(), this.getEmailConstraint()).toArray(new Constraint[4]);
    }

    public static class Builder {
        private Constraint<Range<Integer>> accountIdConstraint;
        private Constraint<String> usernameConstraint;
        private Constraint<String> passwordConstraint;
        private Constraint<String> emailConstraint;

        public Builder() {
            this.accountIdConstraint = null;
            this.usernameConstraint = null;
            this.passwordConstraint = null;
            this.emailConstraint = null;
        }

        public Builder username(final String username) {
            this.usernameConstraint = new Constraint<>(Operation.IS, true, username, "username");
            return this;
        }

        public Builder notUsername(final String username) {
            this.usernameConstraint = new Constraint<>(Operation.IS, false, username, "username");
            return this;
        }

        public Builder usernameLike(final String username) {
            this.usernameConstraint = new Constraint<>(Operation.LIKE, true, username, "username");
            return this;
        }

        public Builder usernameNotLike(final String username) {
            this.usernameConstraint = new Constraint<>(Operation.LIKE, false, username, "username");
            return this;
        }

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

正如你所看到的那样 AccountConstraint.Builder.username（String s）和 AccountConstraint.Builder.notUsername（String s）之间的细微差别。

As you can see there is very subtle difference between AccountConstraint.Builder.username(String s) and AccountConstraint.Builder.notUsername(String s).

我希望能够写出类似的新AccountConstraint.Builder（）。not（username（s））; 。但是，如果在调用Java类中未定义 username（String s），我知道这不是有效的Java语法。我不想再次重复整个 AccountConstraint.Builder（）来到达用户名（String s）部分。任何解决方案？

I would like to be able to write something like new AccountConstraint.Builder().not(username(s));. However as I know this is not valid Java syntax if username(String s) is not defined in the calling Java class. I neither wish to repeat the whole AccountConstraint.Builder() again to reach the username(String s) part. Any solutions?

第二个问题：可以 AccountConstraint.getConstraints（）改进或编写更简单吗？

Second question: Can AccountConstraint.getConstraints() be improved or written more simple?

问候。

推荐答案

你可以而不是构建器的一个方法，设置一个标志，然后否定下一个约束。

you could make not a method of your builder, setting a flag, which then negates the next constraint.

private boolean negate = false;

public Builder not() {
    negate = true;
}

public Builder username(final String username) {
    this.usernameConstraint = new Constraint<>(Operation.IS, !negate, username, "username");
    negate = false;
    return this;
}

这篇关于Java改进特定类的Builder模式的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！