Spring 内置工具类总结

╰+哭是因爲堅強的太久メ 2022-10-29 03:23 193阅读 0赞

## 内置类搜索 ##

可以通过进入IDE并在`*Utils`类搜索或`*Utils.java`文件搜索中进行搜索来找到它们  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FidTkzNTAwOTA2Ng_size_16_color_FFFFFF_t_70]

## 常用 ##

让我们看看其中的一些。

*  `BeanUtils` \-处理JavaBeans的有用功能
 *  `ClassUtils` \-有用的功能，用于反思性地询问类型
 *  `SystemPropertyUtils`\-处理`System`属性的有用功能
 *  `FileCopyUtils`\-用于复制`InputStream`和`OutputStream`实现的有用功能
 *  `AopUtils` \-处理Spring的AOP代理的有用功能
 *  `ReflectionUtils` \-广泛用于处理反思的有用功能
 *  `Assert` \-有用的功能，有助于按合同设计的断言
 *  `CollectionUtils`\-用于处理各种Java`java.util.Collection`类型的有用函数
 *  `SerializeUtils` \-用于Java序列化的有用功能

package bootiful.utils;
    
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.extern.log4j.Log4j2;
    import org.springframework.aop.support.AopUtils;
    import org.springframework.beans.BeanUtils;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.context.event.ApplicationReadyEvent;
    import org.springframework.context.ApplicationListener;
    import org.springframework.context.annotation.Bean;
    import org.springframework.core.ResolvableType;
    import org.springframework.core.io.ClassPathResource;
    import org.springframework.core.io.Resource;
    import org.springframework.jmx.support.JmxUtils;
    import org.springframework.stereotype.Component;
    import org.springframework.util.*;
    
    import javax.annotation.PostConstruct;
    import java.beans.PropertyDescriptor;
    import java.io.InputStreamReader;
    import java.io.Reader;
    import java.io.Serializable;
    import java.lang.reflect.Constructor;
    import java.lang.reflect.Field;
    import java.util.*;
    
    @Log4j2
    @SpringBootApplication
    public class BootifulApplication { 
    
    	@Data
    	@AllArgsConstructor
    	@Component
    	public static class DemoClass { 
    
    		@PostConstruct
    		public void begin() { 
    			log.info("begin()");
    		}
    
    		private final List<Map<String, Object>> list = new ArrayList<>();
    
    	}
    
    	@Bean
    	ApplicationListener<ApplicationReadyEvent> ready(DemoClass demo) { 
    		return event -> { 
    
    			Assert.notNull(demo.getList(), "the list can't be null");
    
    			beansUtils(demo);
    			classUtils();
    			systemPropertyUtils();
    			fileCopyUtils();
    			aop(demo);
    			reflection();
    			ensure();
    			collections();
    			serialize();
    
    		};
    	}
    
    	private void ensure() { 
    		int counter = 2;
    		Assert.state(counter == 2, () -> "the counter should be 2 or more. Was " + counter);
    		Assert.hasText("Hello, world!", () -> "this string should be a non-null, non-empty String");
    	}
    
    	private void reflection() { 
    
    		ReflectionUtils.doWithFields(DemoClass.class, field -> log.info("field = " + field.toString()));
    		ReflectionUtils.doWithMethods(DemoClass.class, method -> log.info("method = " + method.toString()));
    
    		Field list = ReflectionUtils.findField(DemoClass.class, "list");
    		log.info(Objects.requireNonNull(list).toString());
    
    		ResolvableType rt = ResolvableType.forField(list);
    		log.info(rt.toString());
    	}
    
    	private void aop(DemoClass demoClass) { 
    		Class<?> targetClass = AopUtils.getTargetClass(demoClass);
    		log.info("Class<?> is " + targetClass);
    		log.info("is AOP proxy? " + AopUtils.isAopProxy(demoClass));
    		log.info("is CGlib proxy? " + AopUtils.isCglibProxy(demoClass));
    	}
    
    	private void collections() { 
    		Collection<String> names = Arrays.asList("Tammie", "Kimly", "Josh");
    		boolean contains = CollectionUtils.containsAny(names, Arrays.asList("Josh"));
    		Assert.state(contains, () -> "one or more of the names in " + names.toString() + " should be present");
    	}
    
    	private void serialize() { 
    		Customer in = new Customer(593232329, "Josh");
    		byte[] bytes = SerializationUtils.serialize(in);
    		Customer out = (Customer) SerializationUtils.deserialize(bytes);
    		Assert.state(out.getId() == in.getId() && out.getName().equals(in.getName()),
    				() -> "the " + Customer.class.getName() + " did not serialize correctlyy");
    	}
    
    	private void fileCopyUtils() { 
    		Resource cpr = new ClassPathResource("/application.properties");
    		try (Reader r = new InputStreamReader(cpr.getInputStream())) { 
    			String contents = FileCopyUtils.copyToString(r);
    			log.info("application.properties contents: " + contents);
    		}
    		catch (Exception e) { 
    			throw new RuntimeException(e);
    		}
    	}
    
    	private void systemPropertyUtils() { 
    		String resolvedText = SystemPropertyUtils.resolvePlaceholders("my home directory is ${user.home}");
    		log.info("resolved text: " + resolvedText);
    	}
    
    	private void classUtils() { 
    		Constructor<DemoClass> demoClassConstructor = ClassUtils.getConstructorIfAvailable(DemoClass.class);
    		log.info("demoClassConstructor: " + demoClassConstructor);
    		try { 
    			DemoClass demoClass = demoClassConstructor.newInstance();
    			log.info("newInstance'd demoClass: " + demoClass);
    		}
    		catch (Exception e) { 
    			throw new RuntimeException(e);
    		}
    	}
    
    	private void beansUtils(DemoClass demo) { 
    		PropertyDescriptor[] descriptors = BeanUtils.getPropertyDescriptors(demo.getClass());
    		for (PropertyDescriptor pd : descriptors) { 
    			log.info("pd: " + pd.getName());
    		}
    	}
    
    	public static void main(String[] args) { 
    		SpringApplication.run(BootifulApplication.class, args);
    	}
    
    }
    
    @Data
    class Customer implements Serializable { 
    
    	static final long serialVersionUID = 1L;
    
    	private int id;
    
    	private String name;
    
    	public Customer(int id, String name) { 
    		this.id = id;
    		this.name = name;
    	}
    
    }

参考：  
https://spring.io/blog/2021/01/27/ymnnalft-the-spring-utils-classes

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