java – 在单独的类中保持构建器(流畅的界面)
作者：互联网
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.是否有任何方法可以保持Foo类和Builder类分离,同时享受上述代码等命名参数的好处？
以下是典型设置：
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;
}
解决方法:
使用成分.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.
例如,在Builder内部使用Foo类而不是每个Foo属性.
简单的代码片段：
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.com","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.com:1111111111:2222222222
说明：
> FaceBookUser是一个复杂的对象,使用组合具有以下属性：
String userName;
UserBasicInfo userInfo;
ContactInfo contactInfo;
> FaceBookUserBuilder是一个静态构建器类,它包含并构建FaceBookUser.
> userName只是构建FaceBookUser的必需参数
> FaceBookUserBuilder通过设置可选参数来构建FaceBookUser：UserBasicInfo和ContactInfo
>此示例说明了使用Builder构建的具有不同属性的三种不同FaceBookUser.
> fbUser1仅作为FaceBookUser构建,仅具有userName属性
> fbUser2使用userName和UserBasicInfo构建为FaceBookUser
> fbUser3使用userName,UserBasicInfo和ContactInfo构建为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.
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.不是在Builder中再次添加所有这些成员变量,而是在Builder类中包含FaceBookUser.
为简单起见,我添加了两个类：UserBasicInfo和ContactInfo.现在使用其他属性来爆炸这个FaceBookUser类
NewsFeed
Messages
Friends
Albums
Events
Games
Pages
Ads
等等
如果在Builder和FaceBookUser中复制所有这些属性,代码将变得难以管理.相反,通过在FaceBookUserBuilder本身使用FaceBookUser的组合,您可以简单地构建过程.
添加上述属性后,您将像往常一样逐步构建FaceBookUser.
它会是这样的：
FaceBookUser fbUser3 = new FaceBookUser.FaceBookUserBuilder("Ravindra").
setUserBasicInfo(info).
setNewsFeed(newsFeed).
setMessages(messages).
setFriends(friends).
setAlbums(albums).
setEvents(events).
setGames(games).
setAds(ads).build();
标签：fluent,builder-pattern,java,design-patterns 来源： https://codeday.me/bug/20190926/1820064.html