I'm looking for a more abstract pattern for builders that handles required fields without the need of writing a validator that checks if all requried fields are set.
I like this builder. But is there a way to make the interfaces more abstract so that I don't need to create a new interface for each required field?
public class Example {
private String first;
private String second;
private String third;
private String fourth;
private String fifth;
public static RequiredSecond builder(String first) {
return new ExampleBuilder(first);
}
public interface RequiredSecond {
RequiredThird withSecond(String second);
}
public interface RequiredThird {
RequiredFourth withThird(String third);
}
public interface RequiredFourth {
Build withFourth(String fourth);
}
public interface Build {
Build withFifth(String fifth);
Example build();
}
private static class ExampleBuilder implements RequiredSecond, RequiredThird, RequiredFourth, Build {
Example example = new Example();
public ExampleBuilder(String first) {
example.setFirst(first);
}
@Override
public Build withFifth(String fifth) {
example.setFifth(fifth);
return this;
}
@Override
public Example build() {
return example;
}
@Override
public Build withFourth(String fourth) {
example.setFourth(fourth);
return this;
}
@Override
public RequiredFourth withThird(String third) {
example.setThird(third);
return this;
}
@Override
public RequiredThird withSecond(String second) {
example.setSecond(second);
return this;
}
}
public String getFirst() {
return first;
}
public void setFirst(String first) {
this.first = first;
}
public String getSecond() {
return second;
}
public void setSecond(String second) {
this.second = second;
}
public String getThird() {
return third;
}
public void setThird(String third) {
this.third = third;
}
public String getFourth() {
return fourth;
}
public void setFourth(String fourth) {
this.fourth = fourth;
}
public String getFifth() {
return fifth;
}
public void setFifth(String fifth) {
this.fifth = fifth;
}
@Override
public String toString() {
return "Example [first=" + first + ", second=" + second + ", third=" + third + ", fourth=" + fourth +
", fifth=" + fifth + "]";
}
}
public class Labb {
public static void main(String[] args) {
// All required including optional
Example ex1 = Example.builder("first").withSecond("second").withThird("third").withFourth("fourth").withFifth("optional fith").build();
System.out.println(ex1);
// Output: Example [first=first, second=second, third=third, fourth=fourth, fifth=optional fith]
// All required excluding optional
Example ex2 = Example.builder("first").withSecond("second").withThird("third").withFourth("fourth").build();
System.out.println(ex2);
// Output: Example [first=first, second=second, third=third, fourth=fourth, fifth=null]
}
}
