将构建器保持在单独的类中（流畅的界面）

本文介绍了将构建器保持在单独的类中（流畅的界面）的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 Foo foo = Foo.builder() .setColor(red) .setName("Fred") .setSize(42) .build();

所以我知道在调用方法时有以下Builder解决方案用于创建命名参数。虽然，这似乎只适用于内部静态类作为构建器，或者我错了吗？我看了一些构建器模式的教程，但是对于我想要做的事情，它们看起来非常复杂。有没有办法让Foo类和Builder类分开，同时享受上述代码等命名参数的好处？

So I know there is the following "Builder" solution for creating named parameters when calling a method. Although, this only seems to work with inner static classes as the builder or am I wrong? I had a look at some tutorials for builder pattern but they seem really complex for what im trying to do. Is there any way to keep the Foo class and Builder class separate while having the benefit of named parameters like the code above?

典型设置下方：

public class Foo { public static class Builder { public Foo build() { return new Foo(this); } public Builder setSize(int size) { this.size = size; return this; } public Builder setColor(Color color) { this.color = color; return this; } public Builder setName(String name) { this.name = name; return this; } // you can set defaults for these here private int size; private Color color; private String name; } public static Builder builder() { return new Builder(); } private Foo(Builder builder) { size = builder.size; color = builder.color; name = builder.name; } private final int size; private final Color color; private final String name; }

推荐答案

使用构图。为了使事情更简单，更清晰，请不要复制源（ Foo ）和构建器（ Builder ）类中的所有属性。

Use composition. To make things easier and cleaner, do not replicate all attributes in source (Foo) and builder (Builder) class.

例如，在 Builder 中改为 Foo 类每个 Foo 属性。

For example, have Foo class inside Builder instead of each of Foo attribute.

简单代码片段：

import java.util.*; class UserBasicInfo{ String nickName; String birthDate; String gender; public UserBasicInfo(String name,String date,String gender){ this.nickName = name; this.birthDate = date; this.gender = gender; } public String toString(){ StringBuilder sb = new StringBuilder(); sb.append("Name:DOB:Gender:").append(nickName).append(":").append(birthDate).append(":"). append(gender); return sb.toString(); } } class ContactInfo{ String eMail; String mobileHome; String mobileWork; public ContactInfo(String mail, String homeNo, String mobileOff){ this.eMail = mail; this.mobileHome = homeNo; this.mobileWork = mobileOff; } public String toString(){ StringBuilder sb = new StringBuilder(); sb.append("email:mobile(H):mobile(W):").append(eMail).append(":").append(mobileHome).append(":").append(mobileWork); return sb.toString(); } } class FaceBookUser { String userName; UserBasicInfo userInfo; ContactInfo contactInfo; public FaceBookUser(String uName){ this.userName = uName; } public void setUserBasicInfo(UserBasicInfo info){ this.userInfo = info; } public void setContactInfo(ContactInfo info){ this.contactInfo = info; } public String getUserName(){ return userName; } public UserBasicInfo getUserBasicInfo(){ return userInfo; } public ContactInfo getContactInfo(){ return contactInfo; } public String toString(){ StringBuilder sb = new StringBuilder(); sb.append("|User|").append(userName).append("|UserInfo|").append(userInfo).append("|ContactInfo|").append(contactInfo); return sb.toString(); } static class FaceBookUserBuilder{ FaceBookUser user; public FaceBookUserBuilder(String userName){ this.user = new FaceBookUser(userName); } public FaceBookUserBuilder setUserBasicInfo(UserBasicInfo info){ user.setUserBasicInfo(info); return this; } public FaceBookUserBuilder setContactInfo(ContactInfo info){ user.setContactInfo(info); return this; } public FaceBookUser build(){ return user; } } } public class BuilderPattern{ public static void main(String args[]){ FaceBookUser fbUser1 = new FaceBookUser.FaceBookUserBuilder("Ravindra").build(); // Mandatory parameters UserBasicInfo info = new UserBasicInfo("sunrise","25-May-1975","M"); // Build User name + Optional Basic Info FaceBookUser fbUser2 = new FaceBookUser.FaceBookUserBuilder("Ravindra"). setUserBasicInfo(info).build(); // Build User name + Optional Basic Info + Optional Contact Info ContactInfo cInfo = new ContactInfo("xxx@xyz","1111111111","2222222222"); FaceBookUser fbUser3 = new FaceBookUser.FaceBookUserBuilder("Ravindra"). setUserBasicInfo(info). setContactInfo(cInfo).build(); System.out.println("Facebook user 1:"+fbUser1); System.out.println("Facebook user 2:"+fbUser2); System.out.println("Facebook user 3:"+fbUser3); } }

输出：

Facebook user 1:|User|Ravindra|UserInfo|null|ContactInfo|null Facebook user 2:|User|Ravindra|UserInfo|Name:DOB:Gender:sunrise:25-May-1975:M|ContactInfo|null Facebook user 3:|User|Ravindra|UserInfo|Name:DOB:Gender:sunrise:25-May-1975:M|ContactInfo|email:mobile(H):mobile(W):xxx@xyz:1111111111:2222222222

说明：

FaceBookUser 是一个复杂的对象，其中包含以下属性：

FaceBookUser is a complex object with below attributes using composition: String userName; UserBasicInfo userInfo; ContactInfo contactInfo;

FaceBookUserBuilder 是一个静态构建器class，包含并构建 FaceBookUser 。

FaceBookUserBuilder is a static builder class, which contains and builds FaceBookUser.

userName只是构建FaceBookUser的必需参数

userName is only Mandatory parameter to build FaceBookUser

FaceBookUserBuilder 通过设置可选参数来构建 FaceBookUser ： code> UserBasicInfo 和 ContactInfo

FaceBookUserBuilder builds FaceBookUser by setting optional parameters : UserBasicInfo and ContactInfo

此示例说明三不同的 FaceBookUsers 具有不同的属性，由Builder构建。

This example illustrates three different FaceBookUsers with different attributes, built from Builder.

fbUser1构建为FaceBookUser仅限userName属性

fbUser2构建为具有userName和UserBasicInfo的FaceBookUser

fbUser3构建为具有userName，UserBasicInfo和ContactInfo的FaceBookUser

在此示例中，使用了合成而不是在Builder类中复制FaceBookUser的所有属性。

In this example, composition has been used instead of duplicating all attributes of FaceBookUser in Builder class.

编辑：

将所有相关属性分组为逻辑类。在FaceBookUser中定义所有这些类。而不是在 Builder 中再次添加所有这些成员变量，而是在 Builder 上课。

Group all related attributes into logical classes. Define all these classes in FaceBookUser. Instead of adding all these member variables again in Builder, contain FaceBookUser in Builder class.

为简单起见，我添加了两个类：UserBasicInfo和ContactInfo。现在将这个FaceBookUser类与其他属性一起爆炸，例如

For simplicity, I have added two classes: UserBasicInfo and ContactInfo . Now explode this FaceBookUser class with other attributes like

NewsFeed Messages Friends Albums Events Games Pages Ads

等。

如果您在 Builder 和 FaceBookUser ，代码将变得难以管理。相反，通过在 FaceBookUserBuilder 中使用 FaceBookUser 的组合，您可以简单地构建流程。

If you duplicate all these attributes in both Builder and FaceBookUser, code will become difficult to manage. Instead, by using composition of FaceBookUser in FaceBookUserBuilder itself, you can simply construction process.

添加上述属性后，您将像往常一样逐步构建 FaceBookUser 。

Once you add above attributes, you will build FaceBookUser in step-by-step process as usual.

它将是这样的：

FaceBookUser fbUser3 = new FaceBookUser.FaceBookUserBuilder("Ravindra"). setUserBasicInfo(info). setNewsFeed(newsFeed). setMessages(messages). setFriends(friends). setAlbums(albums). setEvents(events). setGames(games). setAds(ads).build();