ConstraintDefinition (Carbonado 1.2.3 API)

+
+

@Documented
+@Retention(value=RUNTIME)
+@Target(value=ANNOTATION_TYPE)
+public @interface ConstraintDefinition

Allows annotations to be defined that restrict property values. The + annotation is just a pointer to a constraint checking class. If the + constraint class is not explicitly provided, it defaults to a static inner + class named "Constraint" in the annotation itself. + +

The constraint class must have a public constructor that accepts the + annotation that has the ConstraintDefinition annotation. It must also define + several "constrain" methods which perform constraint checks on specific + property types. +

+ Example integer constraint: +

+ @Documented
+ @Retention(RetentionPolicy.RUNTIME)
+ @Target(ElementType.METHOD)
+ @ConstraintDefinition
+ public @interface IntegerConstraint {
+     int min() default Integer.MIN_VALUE;
+
+     int max() default Integer.MAX_VALUE;
+
+     public static class Constraint {
+         private final String propertyName;
+         private final int min;
+         private final int max;
+
+         // Constructor may throw a MalformedTypeException if
+         // params supplied by annotation are illegal.
+
+         /**
+          * @param type optional type of object that contains the constrained property
+          * @param propertyName name of property with constraint
+          * @param annotation specific annotation that binds to this constraint class
+          */
+         public Constraint(Class type, String propertyName, IntegerConstraint annotation) {
+             this.propertyName = propertyName;
+             this.min = annotation.min();
+             this.max = annotation.max();
+         }
+
+         // Define a constrain method for each supported property type.
+
+         /**
+          * @param propertyValue specific value to constrain
+          */
+         public void constrain(int propertyValue) throws IllegalArgumentException {
+             if (propertyValue < min || propertyValue > max) {
+                 throw new IllegalArgumentException
+                     ("Value for \"" + propertyName + "\" must be in range " +
+                      min + ".." + max + ": " + propertyValue);
+             }
+         }
+     }
+ }
+

+ + The newly defined integer constraint can be applied to property mutators. + +

+ public interface UserInfo extends Storable {
+     ...
+
+     int getAge();
+     // Constraint is called before setting age.
+     @IntegerConstraint(min=0, max=120)
+     void setAge(int value);
+ }
+

Author:: Brian S O'Neill

+ +
- + + +
  Optional Element Summary
  + + + + + + + + + + +
  Optional Elements
  Modifier and Type Optional Element and Description
  java.lang.Class implementation +
  Specify class which will perform constraint checking.
  +
  +
+

Optional Elements
Modifier and Type	Optional Element and Description
`java.lang.Class`	`implementation` + Specify class which will perform constraint checking. +

+ +
- + + +
  Element Detail
  + + + +
  - +
    implementation
    +
```
public abstract java.lang.Class implementation
```
    +
    Specify class which will perform constraint checking. Must have a public + constructor with the signature + (Class type, String propertyName, Annotation), + where Annotation refers to the annotation with the + constraint definition. + +
    The implementation class need not be explicitly specified. By + default, the constraint class must be a static inner class of the + annotation, named "Constraint".
    +
    +
    Default:
    +
    void.class
    +
    +
  +
+

Annotation Type ConstraintDefinition

Optional Element Summary

Element Detail

implementation