Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Replace Validatable by a generic type parameter T to make the validation framework type safe.</p> <pre><code>public interface Rule&lt;T&gt; { public List&lt;ValidationError&gt; check(T value); } </code></pre> <p>Let's extend our framework with an interface ValidationStrategy:</p> <pre><code>public interface ValidationStrategy&lt;T&gt; { public List&lt;Rule&lt;? super T&gt;&gt; getRules(); } </code></pre> <p>We are dealing with rules bounded by "? super T" so we can add a rule for Animal to a Dog Validator (assuming Dog extends Animal). The Validator now looks like this:</p> <pre><code>public class Validator&lt;T&gt; implements Rule&lt;T&gt; { private List&lt;Rule&lt;? super T&gt;&gt; tests = new ArrayList&lt;Rule&lt;? super T&gt;&gt;(); public Validator(ValidationStrategy&lt;T&gt; type) { this.tests = type.getRules(); } public void addRule(Rule&lt;? super T&gt; rule) { tests.add(rule); } public List&lt;ValidationError&gt; check(T value) { List&lt;ValidationError&gt; list = new ArrayList&lt;ValidationError&gt;(); for (Rule&lt;? super T&gt; rule : tests) { list.addAll(rule.check(value)); } return list; } } </code></pre> <p>Now we can implement a sample DogValidationStrategy like this:</p> <pre><code>public class DogValidationStrategy implements ValidationStrategy&lt;Dog&gt; { public List&lt;Rule&lt;? super Dog&gt;&gt; getRules() { List&lt;Rule&lt;? super Dog&gt;&gt; rules = new ArrayList&lt;Rule&lt;? super Dog&gt;&gt;(); rules.add(new Rule&lt;Dog&gt;() { public List&lt;ValidationError&gt; check(Dog dog) { // dog check... return Collections.emptyList(); } }); rules.add(new Rule&lt;Animal&gt;() { public List&lt;ValidationError&gt; check(Animal animal) { // animal check... return Collections.emptyList(); } }); return rules; } } </code></pre> <p>Or, like in your sample, we may have an Enum providing several dog validation strategies:</p> <pre><code>public enum DogValidationType implements ValidationStrategy&lt;Dog&gt; { STRATEGY_1 { public List&lt;Rule&lt;? super Dog&gt;&gt; getRules() { // answer rules... } }, // more dog validation strategies } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POComposite Strategy pattern - java - How bad is this code?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USchris
    1. USchris
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POComposite Strategy pattern - java - How bad is this code?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTBountyClose
    1. CO@chris Thank you, your answer helps. I have one question. In Dog ValidationStrategy, I would like ? extends Animal not ? super Dog. This would ensure that a single rule can be applied to Dog and Cat. Now, when I try declaring everything as T extends Animal, compiler complains about the for loop in Validator class. I get this error message: The method check(capture-of ? extends Animal) in the type Rule<capture-of ? extends Animal> is not applicable for the arguments (T)
      singulars
      1. PO
      1. USJay
    2. CO@chris your answer is the closest to what I want, if you can answer my comment, I will accept your answer.
      singulars
      1. PO
      1. USJay
    3. COJay, if a rule is meant to be applied to dogs *and* cats, shouldn't that be an animal rule? If you could do what you described, a cat rule may be passed in a dog in check(animal).
      singulars
      1. PO
      1. USchris
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload