Improve builder pattern on validation check?

Question

I recently started using Builder pattern in one of my projects and I am trying to add some sort of validations on my Builder class. I am assuming we cannot do this at compile time so that's why I am doing this validation at runtime. But may be I am wrong and that's what I am trying to see whether I can do this at compile time.

public final class RequestKey {

    private final Long userid;
    private final String deviceid;
    private final String flowid;
    private final int clientid;
    private final long timeout;
    private final boolean abcFlag;
    private final boolean defFlag;
    private final Map<String, String> baseMap;

    private RequestKey(Builder builder) {
        this.userid = builder.userid;
        this.deviceid = builder.deviceid;
        this.flowid = builder.flowid;
        this.clientid = builder.clientid;
        this.abcFlag = builder.abcFlag;
        this.defFlag = builder.defFlag;
        this.baseMap = builder.baseMap.build();
        this.timeout = builder.timeout;
    }

    public static class Builder {
        protected final int clientid;
        protected Long userid = null;
        protected String deviceid = null;
        protected String flowid = null;
        protected long timeout = 200L;
        protected boolean abcFlag = false;
        protected boolean defFlag = true;
        protected ImmutableMap.Builder<String, String> baseMap = ImmutableMap.builder();

        public Builder(int clientid) {
            checkArgument(clientid > 0, "clientid must not be negative or zero");
            this.clientid = clientid;
        }

        public Builder setUserId(long userid) {
            checkArgument(userid > 0, "userid must not be negative or zero");
            this.userid = Long.valueOf(userid);
            return this;
        }

        public Builder setDeviceId(String deviceid) {
            checkNotNull(deviceid, "deviceid cannot be null");
            checkArgument(deviceid.length() > 0, "deviceid can't be an empty string");
            this.deviceid = deviceid;
            return this;
        }

        public Builder setFlowId(String flowid) {
            checkNotNull(flowid, "flowid cannot be null");
            checkArgument(flowid.length() > 0, "flowid can't be an empty string");
            this.flowid = flowid;
            return this;
        }

        public Builder baseMap(Map<String, String> baseMap) {
            checkNotNull(baseMap, "baseMap cannot be null");
            this.baseMap.putAll(baseMap);
            return this;
        }

        public Builder abcFlag(boolean abcFlag) {
            this.abcFlag = abcFlag;
            return this;
        }

        public Builder defFlag(boolean defFlag) {
            this.defFlag = defFlag;
            return this;
        }

        public Builder addTimeout(long timeout) {
            checkArgument(timeout > 0, "timeout must not be negative or zero");
            this.timeout = timeout;
            return this;
        }

        public RequestKey build() {
            if (!this.isValid()) {
                throw new IllegalStateException("You have to pass at least one"
                        + " of the following: userid, flowid or deviceid");
            }
            return new RequestKey(this);
        }

        private boolean isValid() {
            return !(TestUtils.isEmpty(userid) && TestUtils.isEmpty(flowid) && TestUtils.isEmpty(deviceid));
        }
    }

    // getters here
}

Problem Statement:

In my above builder pattern, I have only one parameter mandatory clientId and rest of them are optional but I need to have either userid, flowid or deviceid set. If none of those three are set then I am throwing IllegalStateException with an error message as shown above in the code. That check I am doing at runtime. I want to do this check at compile time if possible by any chance and don't build my pattern unless everything is provided?

It is not mandatory that they will pass all those three id's everytime, they can pass all three or sometimes two or sometimes only one but the condition is either one of them should be set.

How can I improve my builder pattern so that I can do id validation at compile time only instead of doing this at runtime?

I found out this SO link which exactly talks about same thing but not sure how can I use it in my scenario? And also this builder pattern with a twist and this SO question

Can anyone provide an example how can I fix this in my builder pattern?

Answer 1

Make build method accessible only if required properties set:

public class Builders {

  /**
   * @param args the command line arguments
   */
  public static void main(String[] args) {

    Builder b = new Builder(123);

//    Builded instance1 = b
//      .defFlag(false)
//      .build(); // compile error

    Builder c1 = b
      .refFlag(true);

    Builded instance2 = b
      .setDeviceId("device id") // here's the magic, without this call `build` method would be unaccessible
      .build();

    Builded instance3 = b
      .refFlag(false)
      .defFlag(true)
      .setDeviceId("device id")
      .setUserId(12)
      .build();

    System.out.printf("%s\n%s\n", instance2, instance3);
  }

}

class Builded implements Cloneable {

  int clientId;

  Long userid;
  String deviceid;
  String flowid;

  boolean defFlag;
  boolean refFlag;

  public Builded(int clientId) {
    this.clientId = clientId;
  }

  @Override
  protected Object clone() throws CloneNotSupportedException {
    return (Builded) super.clone();
  }

  @Override
  public String toString() {
    return String.format("{c: %d, u: %d, d: %s, f: %s, df: %b, rf: %b}", clientId, userid, deviceid, flowid, defFlag, refFlag);
  }

}

class Builder {

  int clientId;
  protected Builded instance;

  private Builder() {
  }

  protected Builder(int clientId) {
    this.clientId = clientId;
    prepare();
  }

  protected final void prepare() {
    instance = new Builded(clientId);
  }

  private Builded build() {
    try {
      return (Builded) instance.clone();
    } catch (CloneNotSupportedException ex) {
      throw new RuntimeException(ex);
    }
  }

  public Builder defFlag(boolean defFlag) {
    instance.defFlag = defFlag;
    return this;
  }

  public Builder refFlag(boolean refFlag) {
    instance.refFlag = refFlag;
    return this;
  }

  public SubBuilder setUserId(long userid) {
    instance.userid = userid;
    return new SubBuilder(instance);
  }

  public SubBuilder setDeviceId(String deviceid) {
    instance.deviceid = deviceid;
    return new SubBuilder(instance);
  }

  public SubBuilder setFlowId(String flowid) {
    instance.flowid = flowid;
    return new SubBuilder(instance);
  }

  public static class SubBuilder extends Builder {

    private SubBuilder(Builded instance) {
      this.instance = instance;
    }

    public Builded build() {
      return super.build();
    }

  }

}

Output:

{c: 123, u: null, d: device id, f: null, df: false, rf: true}
{c: 123, u: 12, d: device id, f: null, df: true, rf: false}