Understanding Rss and atOM utilitiEs (ROME) Bean Utilities

Rome com.sun.syndication.feed.impl package contains a set of Java classes that provide support for all the basic features Java Beans commonly must have: toString, equals, hashcode and cloning.

By using these classes Beans don't have to hand code these functions. This greatly simplifies things when Beans have several properties, collection properties and composite properties.

The CloneableBean, EqualsBean, ToStringBean and ObjectBean classes use instrospection on the properties of the classes using them. This is done recursively on all properties. All ROME Beans default implementations leverage these classes.

ToStringBean

Beans implementing the ToString interface must implement the toString(String prefix) method. This method must print the bean properties names and values, one per per line, separating the name and value with an '=' sign and prefixing the name with the given prefix parameter using the same notation used in the JSP expression language used in JSTL and in JSP 2.0. This must be done recursively for all array, collection and ToString properties.

The ToStringBean class provides an implementation of the toString() method producing a detailed output of all the properties of the Bean being processed. The ToStringBean constructor takes the class definition the ToStringBean class should use for properties scanning -using instrospection- for printing, normally it is the class of the Bean using the ToStringBean.

Using the ToStringBean class

    public class MyBean {

        public Foo getFoo() { ... }
        public void setFoo(Foo foo) { ... }

        public String getName() { ... }
        public void setName(String name) { ... }

        public List getValues() { ... }
        public void setValues(List values) { ... }

        public String toString(String prefix) {
            ToStringBean tsBean = new ToStringBean(MyBean.class,this);
            return tsBean.toString(prefix);
        }

        public String toString() {
            return toString("myBean");
        }
    }

EqualBean

The EqualsBean class provides a recursive introspetion-based implementation of the equals() and hashCode() methods working on the Bean properties. The EqualsBean constructor takes the class definition that should be properties scanned (using introspection) by the equals() and thehashCode() methods. The EqualsBean class works on array, collection, bean and basic type properties.

Using the EqualsBean class

    public class MyBean  {

        public Foo getFoo() { ... }
        public void setFoo(Foo foo) { ... }

        public String getName() { ... }
        public void setName(String name) { ... }

        public List getValues() { ... }
        public void setValues(List values) { ... }

        public boolean equals(Object obj) {
            EqualsBean eBean = new EqualsBean(MyBean.class,this);
            return eBean.beanEquals(obj);
        }

        public int hashCode() {
            EqualsBean equals = new EqualsBean(MyBean.class,this);
            return equals.beanHashCode();
        }
    }

CloneableBean

The CloneableBean class provides a recursive introspetion-based implementation of the clone() method working on the Bean properties. The CloneableBean class works on array, collection, bean and basic type properties.

Using the CloneableBean class

    public class MyBean implements Cloneable {

        public Foo getFoo() { ... }
        public void setFoo(Foo foo) { ... }

        public String getName() { ... }
        public void setName(String name) { ... }

        public List getValues() { ... }
        public void setValues(List values) { ... }

        public Object clone() {
            CloneableBean cBean = new CloneableBean(this);
            return cBean.beanClone();
        }
    }

By default, the CloneableBean copies all properties of the given object. It also supports an ignore-properties set, the property names in this set will not be copied to the cloned instance. This is useful for cases where the Bean has convenience properties (properties that are actually references to other properties or properties of properties). For example SyndFeed and SyndEntry beans have convenience properties, publishedDate, author, copyright and categories all of them mapped to properties in the DC Module.

ObjectBean

The ObjectBean is a convenience bean providing ToStringBean, EqualsBean and CloneableBean functionality support. Also, ObjectBeans implements the Serializable interface making the beans serializable if all its properties are. Beans extending ObjectBean get toString(), equals(),hashCode() and clone() support as defined above.

And example of using the ObjectBean class is:

    public class MyBean extends ObjectBean {

        public MyBean() {
            super(MyBean.class);
        }

        public Foo getFoo() { ... }
        public void setFoo(Foo foo) { ... }

        public String getName() { ... }
        public void setName(String name) { ... }

        public List getValues() { ... }
        public void setValues(List values) { ... }
    }

It can also be used in delegation mode instead as some of the previous examples.