Java 自定义注解例子

小鱼儿 2022-08-09 16:37 160阅读 0赞

在这篇文章中，我将展示怎么创建两个自定义的注解-@Test和TestInfo，来模拟一件的单元测试的框架

补充：这个单元测试的例子是受官方文档的启发。[这篇][Link 1]。

### @Test注解 ###

这个@interface标志Java这是一个自定义的标签，然后你可以在方法上像@Test（enable=false）这样添加注解

package com.mkyong.test.core;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD) //只能在方法上使用
    public @interface Test {
    	
    	//should ignore this test?
    	public boolean enabled() default true;
    	
    }

注意：方法的声明不能有任何参数或者抛出异常，返回值的类型要限制在原始值，String、Class、enums、annotations和数组类型

### @TesterInfo注解 ###

这个@TesterInfo是应用在类层面上的，存储测试类的细节，这展示了enum、array和String不同返回值的用法

package com.mkyong.test.core;
    
    import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.TYPE) //类级别
    public @interface TesterInfo {
    
    	public enum Priority {
    	   LOW, MEDIUM, HIGH
    	}
    
    	Priority priority() default Priority.MEDIUM;
    	
    	String[] tags() default "";
    	
    	String createdBy() default "Mkyong";
    	
    	String lastModified() default "03/01/2014";
    
    }

### 单元测试的例子 ###

创建一个单元测试的例子，使用新自定义的注解@Test和@TesterInfo注解这个例子

package com.mkyong.test;
    
    import com.mkyong.test.core.Test;
    import com.mkyong.test.core.TesterInfo;
    import com.mkyong.test.core.TesterInfo.Priority;
    
    @TesterInfo(
    	priority = Priority.HIGH, 
    	createdBy = "mkyong.com",  
    	tags = {"sales","test" }
    )
    public class TestExample {
    
    	@Test
    	void testA() {
    	  if (true)
    		throw new RuntimeException("This test always failed");
    	}
    
    	@Test(enabled = false)
    	void testB() {
    	  if (false)
    		throw new RuntimeException("This test always passed");
    	}
    
    	@Test(enabled = true)
    	void testC() {
    	  if (10 > 1) {
    		// do nothing, this test always passed.
    	  }
    	}
    
    }

### Java反射，读取这个注解 ###

下边这个例子展示怎么使用Java反射读取和处理自定义的注解

package com.mkyong.test;
    
    import java.lang.annotation.Annotation;
    import java.lang.reflect.Method;
    
    import com.mkyong.test.core.Test;
    import com.mkyong.test.core.TesterInfo;
    
    public class RunTest {
    
      public static void main(String[] args) throws Exception {
    
    	System.out.println("Testing...");
    
    	int passed = 0, failed = 0, count = 0, ignore = 0;
    
    	Class<TestExample> obj = TestExample.class;
    
    	// Process @TesterInfo
    	if (obj.isAnnotationPresent(TesterInfo.class)) {
    
    		Annotation annotation = obj.getAnnotation(TesterInfo.class);
    		TesterInfo testerInfo = (TesterInfo) annotation;
    
    		System.out.printf("%nPriority :%s", testerInfo.priority());
    		System.out.printf("%nCreatedBy :%s", testerInfo.createdBy());
    		System.out.printf("%nTags :");
    
    		int tagLength = testerInfo.tags().length;
    		for (String tag : testerInfo.tags()) {
    			if (tagLength > 1) {
    				System.out.print(tag + ", ");
    			} else {
    				System.out.print(tag);
    			}
    			tagLength--;
    		}
    
    		System.out.printf("%nLastModified :%s%n%n", testerInfo.lastModified());
    
    	}
    
    	// Process @Test
    	for (Method method : obj.getDeclaredMethods()) {
    
    		// if method is annotated with @Test
    		if (method.isAnnotationPresent(Test.class)) {
    
    			Annotation annotation = method.getAnnotation(Test.class);
    			Test test = (Test) annotation;
    
    			// if enabled = true (default)
    			if (test.enabled()) {
    
    			  try {
    				method.invoke(obj.newInstance());
    				System.out.printf("%s - Test '%s' - passed %n", ++count, method.getName());
    				passed++;
    			  } catch (Throwable ex) {
    				System.out.printf("%s - Test '%s' - failed: %s %n", ++count, method.getName(), ex.getCause());
    				failed++;
    			  }
    
    			} else {
    				System.out.printf("%s - Test '%s' - ignored%n", ++count, method.getName());
    				ignore++;
    			}
    
    		}
    
    	}
    	System.out.printf("%nResult : Total : %d, Passed: %d, Failed %d, Ignore %d%n", count, passed, failed, ignore);
    
    	}
    }

输出结果：

Testing...
    
    Priority :HIGH
    CreatedBy :mkyong.com
    Tags :sales, test
    LastModified :03/01/2014
    
    1 - Test 'testA' - failed: java.lang.RuntimeException: This test always failed 
    2 - Test 'testC' - passed 
    3 - Test 'testB' - ignored
    
    Result : Total : 3, Passed: 1, Failed 1, Ignore 1

[Link 1]: http://docs.oracle.com/javase/1.5.0/docs/guide/language/annotations.html