Commons Collections - Transformer组 补充

// transformer setup

        Transformer developerTransformer = new Transformer() {

            public Object transform(Object obj) {

                Applicant app = (Applicant) obj;

                return new Employee(

                    app.getName(), app.getAge(), new Date(), "E4", 2000

                );

            }

        };

        Transformer testerTransformer = new Transformer() {

            public Object transform(Object obj) {

                Applicant app = (Applicant) obj;

                return new Employee(

                    app.getName(), app.getAge(), new Date(), "E4", 2000

                );

            }

        };

        Transformer pmTransformer = new Transformer() {

            public Object transform(Object obj) {

                Applicant app = (Applicant) obj;

                return new Employee(

                    app.getName(), app.getAge(), new Date(), "E5", 3000

                );

            }

        };

        Transformer[] transformers = new Transformer[] {

            developerTransformer,

            testerTransformer,

            pmTransformer

        };

       

        // transform

        Transformer employTransformer = new SwitchTransformer(

            checkApplyFor, transformers, null

        );

        Collection employed = CollectionUtils.collect(appList, employTransformer);

       

        // output

        System.out.println("Applicants: ");

        Iterator iter1 = appList.iterator();

        while (iter1.hasNext()) {

            System.out.println(iter1.next());

        }

        System.out.println("Employed: ");

        Iterator iter2 = employed.iterator();

        while (iter2.hasNext()) {

            System.out.println(iter2.next());

        }

 

        System.out.println(StringUtils.repeat("=", 40));

    }

 

}

 

以下是运行结果：

 

========= demoTransformerUsage =========

Applicants:

Applicant[name=Tony,age=26,applyFor=Developer]

Applicant[name=Michelle,age=24,applyFor=Tester]

Applicant[name=Jack,age=28,applyFor=Project Manager]

Employed:

Employee[name=Tony,age=26,dateJoined=2005-08-05,grade=E4,salary=2000.0]

Employee[name=Michelle,age=24,dateJoined=2005-08-05,grade=E4,salary=2000.0]

Employee[name=Jack,age=28,dateJoined=2005-08-05,grade=E5,salary=3000.0]

========================================

 

我们首先定义一组Predicate，用于在SwitchTransformer中判断采用那个具体的Transformer，这个具体的Transformer也是通过数组同时传递给SwitchTransformer的构造方法的。不同的Predicate可以有不同的实现，不同的Transformer也可以有不同的实现，因为它们之间实际上完全是相互独立的。这就使我们有效的分离了逻辑和具体业务。