多态对象层次结构的构建器模式:Java可能吗?
我有一个接口层次结构,子接口实现父接口。我希望使用不可变对象,因此我希望设计方便地构造这些对象的多态对象层次结构的构建器模式:Java可能吗?,java,design-patterns,builder,Java,Design Patterns,Builder,我有一个接口层次结构,子接口实现父接口。我希望使用不可变对象,因此我希望设计方便地构造这些对象的Builder类。但是,我有许多Child接口,我不想在每种类型的子生成器中重复构建Parents的代码 因此,假设以下定义: public interface Parent { public Long getParentProperty(); } public interface Child1 extends Parent { public Integer getChild1Pro
Builder
类。但是,我有许多Child
接口,我不想在每种类型的子生成器中重复构建Parent
s的代码
因此,假设以下定义:
public interface Parent {
public Long getParentProperty();
}
public interface Child1 extends Parent {
public Integer getChild1Property();
}
public interface Child2 extends Parent {
public String getChild2PropertyA();
public Object getChild2PropertyB();
}
如何有效地实现构建器Child1Builder
和Child2Builder
?它们应支持以下操作:
Child1 child1 = Child1Builder.newChild1().withChild1Property(5).withParentProperty(10L);
及
我不想为每个子生成器实现一个特殊的withParentProperty
编辑以将第二个属性添加到Child2
,以澄清这不能通过简单的泛型实现。我不是在寻找一种方法来组合Child1
和Child2
——我在寻找一种方法来实现一个Builder
系统,它不会重复为每个子类构建父类的工作
谢谢你的帮助 使用泛型,如下所示:
public interface Parent {
public Long getParentProperty();
}
public interface Child<T> {
public T getChildProperty();
}
公共接口父级{
公共长getParentProperty();
}
公共接口子项{
公共T getChildProperty();
}
然后用
Child
代替Child1,用Child2代替Child2,用Child
我想象的解决方案就像CRTP。您可以定义一个基类来处理与父类相关的初始化,但是您仍然会发现两个样板文件getParent()
和getThis()
方法在每个派生的与子类相关的构建器类中重复太多
看一看:
abstract class ParentBase implements Parent
{
@Override
public final Long getParentProperty()
{
return parentProperty_;
}
protected void setParentProperty(Long value)
{
parentProperty_ = value;
}
private Long parentProperty_;
}
abstract class ParentBuilder<T extends ParentBuilder<T>>
{
T withParentProperty(Long value)
{
getParent().setParentProperty(value);
return getThis();
}
protected abstract ParentBase getParent();
protected abstract T getThis();
}
final class ConcreteChild1 extends ParentBase implements Child1
{
@Override
public Integer getChild1Property()
{
return childProperty_;
}
public void setChild1Property(Integer value)
{
childProperty_ = value;
}
private Integer childProperty_;
}
final class Child1Builder extends ParentBuilder<Child1Builder>
{
public Child1Builder()
{
pending_ = new ConcreteChild1();
}
public Child1Builder withChild1Property(Integer value)
{
pending_.setChild1Property(value);
return this;
}
@Override
protected ParentBase getParent()
{
return pending_;
}
@Override
protected Child1Builder getThis()
{
return this;
}
private final ConcreteChild1 pending_;
}
抽象类ParentBase实现父类
{
@凌驾
公共最终长getParentProperty()
{
返回parentProperty;
}
受保护的void setParentProperty(长值)
{
parentProperty=值;
}
私人长父母财产;
}
抽象类父生成器
{
T withParentProperty(长值)
{
getParent().setParentProperty(值);
返回getThis();
}
受保护的抽象ParentBase getParent();
保护抽象T getThis();
}
最后一个类ConcreteChild1扩展了ParentBase,实现了Child1
{
@凌驾
公共整数getChild1Property()
{
归还儿童财产;
}
public void setChild1属性(整数值)
{
childProperty=值;
}
私有整数childProperty;
}
最终类Child1Builder扩展了ParentBuilder
{
公共Child1Builder()
{
挂起=新的ConcreteChild1();
}
具有Child1属性(整数值)的公共Child1生成器
{
挂起。setChild1属性(值);
归还这个;
}
@凌驾
受保护的ParentBase getParent()
{
返回待定;
}
@凌驾
受保护的儿童1生成器getThis()
{
归还这个;
}
私人最终子女1待定;
}
如您所见,ParentBuilder
类型期望与派生类型协作,以允许它返回正确类型的实例。它自己的this
引用不会到期,因为ParentBuilder
中的this
类型当然是ParentBuilder
,而不是要维护“流畅”调用链接的Child1Builder
我把“getThis()
技巧”归功于。没有构建器的情况下可能会这样吗?:
interface P {
public Long getParentProperty();
}
interface C1 extends P {
public Integer getChild1Property();
}
interface C2 extends P {
public String getChild2PropertyA();
public Object getChild2PropertyB();
}
abstract class PABC implements P {
@Override public final Long getParentProperty() {
return parentLong;
}
protected Long parentLong;
protected PABC setParentProperty(Long value) {
parentLong = value;
return this;
}
}
final class C1Impl extends PABC implements C1 {
protected C1Impl setParentProperty(Long value) {
super.setParentProperty(value);
return this;
}
@Override public Integer getChild1Property() {
return n;
}
public C1Impl setChild1Property(Integer value) {
n = value;
return this;
}
private Integer n;
}
final class C2Impl extends PABC implements C2 {
private String string;
private Object object;
protected C2Impl setParentProperty(Long value) {
super.setParentProperty(value);
return this;
}
@Override public String getChild2PropertyA() {
return string;
}
@Override public Object getChild2PropertyB() {
return object;
}
C2Impl setChild2PropertyA(String string) {
this.string=string;
return this;
}
C2Impl setChild2PropertyB(Object o) {
this.object=o;
return this;
}
}
public class Myso9138027 {
public static void main(String[] args) {
C1Impl c1 = new C1Impl().setChild1Property(5).setParentProperty(10L);
C2Impl c2 = new C2Impl().setChild2PropertyA("Hello").setParentProperty(10L).setChild2PropertyB(new Object());
}
}
包SO913802;
导入java.util.*;
导入so9138027take2.C2.name;
接口P{
公共对象getParentProperty(名称);
枚举名称{
i(Integer.class)、d(Double.class)、s(String.class);
名称(类clazz){
this.clazz=clazz;
}
最后一节课;
}
}
接口C1扩展了P{
公共对象getChildProperty(名称);
枚举名称{
a(Integer.class)、b(Double.class)、c(String.class);
名称(类clazz){
this.clazz=clazz;
}
最后一节课;
}
}
接口C2扩展到P{
公共对象getChildProperty(名称);
枚举名称{
x(Integer.class)、y(Double.class)、z(String.class);
名称(类clazz){
this.clazz=clazz;
}
最后一节课;
}
}
抽象类PABCImmutable实现了P{
公共PABCImmutable(PABC父级){
parentNameToValue=Collections.unmodifiableMap(parent.parentNameToValue);
}
@重写公共最终对象getParentProperty(名称){
返回parentNameToValue.get(name);
}
公共字符串toString(){
返回parentNameToValue.toString();
}
最终映射parentNameToValue;
}
抽象类PABC实现了P{
@重写公共最终对象getParentProperty(名称){
返回parentNameToValue.get(name);
}
受保护的PABC setParentProperty(名称、对象值){
if(name.clazz.isInstance(value))parentNameToValue.put(name,value);
其他的
抛出新的RuntimeException(“值对“+name”无效);
归还这个;
}
公共字符串toString(){
返回parentNameToValue.toString();
}
EnumMap parentNameToValue=新的EnumMap(P.Names.class);
}
最后一个类C1Immutable扩展了PABCImmutable实现C1{
公共c1不可变(c1 impl c1){
超级(c1);
nameToValue=Collections.unmodifiableMap(c1.nameToValue);
}
@重写公共对象getChildProperty(C1.name){
返回nameToValue.get(name);
}
公共字符串toString(){
返回super.toString()+nameToValue.toString();
}
最终地图名称和价值;
}
最后一个类C1Impl扩展了PABC实现C1{
@重写公共对象getChildProperty(C1.name){
返回nameToValue.get(name);
}
公共对象setChildProperty(C1.Names名称、对象值){
if(name.clazz.isInstance(value))nameToValue.put(name,value);
其他的
扔
interface P {
public Long getParentProperty();
}
interface C1 extends P {
public Integer getChild1Property();
}
interface C2 extends P {
public String getChild2PropertyA();
public Object getChild2PropertyB();
}
abstract class PABC implements P {
@Override public final Long getParentProperty() {
return parentLong;
}
protected Long parentLong;
protected PABC setParentProperty(Long value) {
parentLong = value;
return this;
}
}
final class C1Impl extends PABC implements C1 {
protected C1Impl setParentProperty(Long value) {
super.setParentProperty(value);
return this;
}
@Override public Integer getChild1Property() {
return n;
}
public C1Impl setChild1Property(Integer value) {
n = value;
return this;
}
private Integer n;
}
final class C2Impl extends PABC implements C2 {
private String string;
private Object object;
protected C2Impl setParentProperty(Long value) {
super.setParentProperty(value);
return this;
}
@Override public String getChild2PropertyA() {
return string;
}
@Override public Object getChild2PropertyB() {
return object;
}
C2Impl setChild2PropertyA(String string) {
this.string=string;
return this;
}
C2Impl setChild2PropertyB(Object o) {
this.object=o;
return this;
}
}
public class Myso9138027 {
public static void main(String[] args) {
C1Impl c1 = new C1Impl().setChild1Property(5).setParentProperty(10L);
C2Impl c2 = new C2Impl().setChild2PropertyA("Hello").setParentProperty(10L).setChild2PropertyB(new Object());
}
}
package so9138027take2;
import java.util.*;
import so9138027take2.C2.Names;
interface P {
public Object getParentProperty(Names name);
enum Names {
i(Integer.class), d(Double.class), s(String.class);
Names(Class<?> clazz) {
this.clazz = clazz;
}
final Class<?> clazz;
}
}
interface C1 extends P {
public Object getChildProperty(Names name);
enum Names {
a(Integer.class), b(Double.class), c(String.class);
Names(Class<?> clazz) {
this.clazz = clazz;
}
final Class<?> clazz;
}
}
interface C2 extends P {
public Object getChildProperty(Names name);
enum Names {
x(Integer.class), y(Double.class), z(String.class);
Names(Class<?> clazz) {
this.clazz = clazz;
}
final Class<?> clazz;
}
}
abstract class PABCImmutable implements P {
public PABCImmutable(PABC parent) {
parentNameToValue = Collections.unmodifiableMap(parent.parentNameToValue);
}
@Override public final Object getParentProperty(Names name) {
return parentNameToValue.get(name);
}
public String toString() {
return parentNameToValue.toString();
}
final Map<Names, Object> parentNameToValue;
}
abstract class PABC implements P {
@Override public final Object getParentProperty(Names name) {
return parentNameToValue.get(name);
}
protected PABC setParentProperty(Names name, Object value) {
if (name.clazz.isInstance(value)) parentNameToValue.put(name, value);
else
throw new RuntimeException("value is not valid for " + name);
return this;
}
public String toString() {
return parentNameToValue.toString();
}
EnumMap<Names, Object> parentNameToValue = new EnumMap<Names, Object>(P.Names.class);
}
final class C1Immutable extends PABCImmutable implements C1 {
public C1Immutable(C1Impl c1) {
super(c1);
nameToValue = Collections.unmodifiableMap(c1.nameToValue);
}
@Override public Object getChildProperty(C1.Names name) {
return nameToValue.get(name);
}
public String toString() {
return super.toString() + nameToValue.toString();
}
final Map<C1.Names, Object> nameToValue;
}
final class C1Impl extends PABC implements C1 {
@Override public Object getChildProperty(C1.Names name) {
return nameToValue.get(name);
}
public Object setChildProperty(C1.Names name, Object value) {
if (name.clazz.isInstance(value)) nameToValue.put(name, value);
else
throw new RuntimeException("value is not valid for " + name);
return this;
}
public String toString() {
return super.toString() + nameToValue.toString();
}
EnumMap<C1.Names, Object> nameToValue = new EnumMap<C1.Names, Object>(C1.Names.class);
}
final class C2Immutable extends PABCImmutable implements C2 {
public C2Immutable(C2Impl c2) {
super(c2);
this.nameToValue = Collections.unmodifiableMap(c2.nameToValue);
}
@Override public Object getChildProperty(C2.Names name) {
return nameToValue.get(name);
}
public String toString() {
return super.toString() + nameToValue.toString();
}
final Map<C2.Names, Object> nameToValue;
}
final class C2Impl extends PABC implements C2 {
@Override public Object getChildProperty(C2.Names name) {
return nameToValue.get(name);
}
public Object setChildProperty(C2.Names name, Object value) {
if (name.clazz.isInstance(value)) {
nameToValue.put(name, value);
} else {
System.out.println("name=" + name + ", value=" + value);
throw new RuntimeException("value is not valid for " + name);
}
return this;
}
public String toString() {
return super.toString() + nameToValue.toString();
}
EnumMap<C2.Names, Object> nameToValue = new EnumMap<C2.Names, Object>(C2.Names.class);
}
public class So9138027take2 {
public static void main(String[] args) {
Object[] parentValues = new Object[] { 1, 2., "foo" };
C1Impl c1 = new C1Impl();
Object[] c1Values = new Object[] { 3, 4., "bar" };
for (P.Names name : P.Names.values())
c1.setParentProperty(name, parentValues[name.ordinal()]);
for (C1.Names name : C1.Names.values())
c1.setChildProperty(name, c1Values[name.ordinal()]);
C2Impl c2 = new C2Impl();
Object[] c2Values = new Object[] { 5, 6., "baz" };
for (P.Names name : P.Names.values())
c2.setParentProperty(name, parentValues[name.ordinal()]);
for (C2.Names name : C2.Names.values())
c2.setChildProperty(name, c2Values[name.ordinal()]);
C1 immutableC1 = new C1Immutable(c1);
System.out.println("child 1: "+immutableC1);
C2 immutableC2 = new C2Immutable(c2);
System.out.println("child 2: "+immutableC2);
}
}
class Parent
{
private final long parentProperty;
public long getParentProperty()
{
return parentProperty;
}
public static abstract class Builder<T extends Parent>
{
private long parentProperty;
public Builder<T> withParentProperty( long parentProperty )
{
this.parentProperty = parentProperty;
return this;
}
public abstract T build();
}
public static Builder<?> builder()
{
return new Builder<Parent>()
{
@Override
public Parent build()
{
return new Parent(this);
}
};
}
protected Parent( Builder<?> builder )
{
this.parentProperty = builder.parentProperty;
}
}
class Child1 extends Parent
{
private final int child1Property;
public int getChild1Property()
{
return child1Property;
}
public static abstract class Builder<T extends Child1> extends Parent.Builder<T>
{
private int child1Property;
public Builder<T> withChild1Property( int child1Property )
{
this.child1Property = child1Property;
return this;
}
public abstract T build();
}
public static Builder<?> builder()
{
return new Builder<Child1>()
{
@Override
public Child1 build()
{
return new Child1(this);
}
};
}
protected Child1( Builder<?> builder )
{
super(builder);
this.child1Property = builder.child1Property;
}
}
class Child2 extends Parent
{
private final String child2PropertyA;
private final Object child2PropertyB;
public String getChild2PropertyA()
{
return child2PropertyA;
}
public Object getChild2PropertyB()
{
return child2PropertyB;
}
public static abstract class Builder<T extends Child2> extends Parent.Builder<T>
{
private String child2PropertyA;
private Object child2PropertyB;
public Builder<T> withChild2PropertyA( String child2PropertyA )
{
this.child2PropertyA = child2PropertyA;
return this;
}
public Builder<T> withChild2PropertyB( Object child2PropertyB )
{
this.child2PropertyB = child2PropertyB;
return this;
}
}
public static Builder<?> builder()
{
return new Builder<Child2>()
{
@Override
public Child2 build()
{
return new Child2(this);
}
};
}
protected Child2( Builder<?> builder )
{
super(builder);
this.child2PropertyA = builder.child2PropertyA;
this.child2PropertyB = builder.child2PropertyB;
}
}
class BuilderTest
{
public static void main( String[] args )
{
Child1 child1 = Child1.builder()
.withChild1Property(-3)
.withParentProperty(5L)
.build();
Child2 grandchild = Child2.builder()
.withChild2PropertyA("hello")
.withChild2PropertyB(new Object())
.withParentProperty(10L)
.build();
}
}