我现有的模型类总是使用这样的构建器模式:
public class Model {
public static class Builder {
private boolean isValid;
private List<String> errorMessagesOrNull;
public Builder setIsValid(final boolean isValid) {
this.isValid = isValid;
return this;
}
public Builder setErrorMessages(final List<String> errorMessages) {
this.errorMessagesOrNull = errorMessages;
return this;
}
public List<String> getErrorMessages() {
return this.errorMessagesOrNull == null ? new ArrayList<>() : this.errorMessagesOrNull;
}
public Model Build() {
return new Model(this);
}
}
private boolean isValid;
private List<String> errorMessages;
private Model(final Builder builder) {
this.isValid = builder.isValid;
this.errorMessages = builder.getErrorMessages();
}
public boolean getIsValid() {
return isValid;
}
public List<String> getErrorMessages() {
return errorMessages;
}
}
如您所见,模型类始终具有 isValid
和 errorMessages
。我想写一个抽象类来最小化那些模型类的重复逻辑。
所以我想出了这个抽象类:
public abstract class AbstractModel<T extends AbstractModel<T>> {
public static abstract class Builder<T> {
private boolean isValid;
private List<String> errorMessagesOrNull;
public Builder<T> setIsValid(final boolean isValid) {
this.isValid = isValid;
return this;
}
public Builder<T> setErrorMessages(final List<String> errorMessages) {
this.errorMessagesOrNull = errorMessages;
return this;
}
public List<String> getErrorMessages() {
return this.errorMessagesOrNull == null ? new ArrayList<>() : this.errorMessagesOrNull;
}
public abstract T Build();
}
private boolean isValid;
private List<String> errorMessages;
private AbstractModel(final Builder<T> builder) {
this.isValid = builder.isValid;
this.errorMessages = builder.getErrorMessages();
}
public boolean getIsValid() {
return isValid;
}
public List<String> getErrorMessages() {
return errorMessages;
}
}
但它并没有真正按照我的预期工作。当我扩展抽象类时:
public class Model extends AbstractModel<Model> {
// Empty here since all fields are extended
}
我不能做这样的事情:
Model model = new Model.Builder.setIsValid(true).Build();
我希望抽象类有Builder
静态类,这样就不用每次都写静态类Builder
请指教。
最佳答案
您还需要实现Builder
。
public class Model extends AbstractModel<Model>{
private Model(final Builder builder) {
super(builder);
}
public static class Builder2 extends AbstractModel.Builder<Model> {
@Override
public Model Build() {
return new Model(this);
}
}
}
然后就可以调用了
Model model = new Model.Builder2().Build();
编辑
此外,AbstractBuilder 的构造函数也必须受到保护
。
protected AbstractModel(final Builder<? extends Builder<T>> builder) {
this.isValid = builder.isValid;
this.errorMessages = builder.getErrorMessages();
}
关于java - builder 模式的抽象类,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/50310891/