Java byte-buddy动态生成子类，Java 动态增加属性和方法

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©Copyright 蕃薯耀 2022-08-31

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Java 使用byte-buddy实现动态生成子类，动态增加属性和方法

一、byte-buddy官网地址

https://bytebuddy.net/

https://github.com/raphw/byte-buddy

二、引入byte-buddy的Maven依赖

		<dependency>
		    <groupId>net.bytebuddy</groupId>
		    <artifactId>byte-buddy</artifactId>
		</dependency>

三、byte-buddy一个简单的例子

Class<?> dynamicType = new ByteBuddy()
  .subclass(Object.class)
  .method(ElementMatchers.named("toString"))
  .intercept(FixedValue.value("Hello World!"))
  .make()
  .load(getClass().getClassLoader())
  .getLoaded();
assertThat(dynamicType.newInstance().toString(), is("Hello World!"));

subclass：声明继承的父类

method：匹配方法

intercept：拦截method匹配后的返回值

四、byte-buddy动态生成子类、属性、方法

	public Object handleEntity(Object data) {
		if(data == null) {
			return data;
		}
		
		ObjectMapper mapper = new ObjectMapper();
        
		String json = "{}";
		try {
			//解决@JsonFormat注解解析不了的问题
			json = mapper.writeValueAsString(data);
			
		} catch (JsonProcessingException e) {
			log.error("Json解析失败：" + e);
			log.error("Json解析失败，data=" + data);
		}
		
		Builder<? extends Object> builder = new ByteBuddy()
				//.redefine(data.getClass())
			  .subclass(data.getClass())
			  //.modifiers(Opcodes.ACC_PUBLIC)
			  //.name("com.builder.vo." + ClassUtil.getClassName(data, true) + "Sub")
			  .name(ClassUtil.getClassName(data, false) + "DynamicTypeBuilder")
		;
		
		
		JSONObject jsonObject = JSONObject.parseObject(json);
		
		for (Field field : ReflectUtil.getFields(data.getClass())) {
			
			Object o = jsonObject.getObject(field.getName(), field.getType());
			
			if(o != null) {
				builder = builder
						//.defineProperty(field.getName(), field.getType())//声明；getter和setter方法
						.method(ElementMatchers.named("get" + StringUtils.capitalize(field.getName())))
						.intercept(FixedValue.value(o))
				;
			}
			
			if (field.getAnnotation(Dict.class) != null) {
				String dictCode = field.getAnnotation(Dict.class).dictCode();
				String dictName = field.getAnnotation(Dict.class).dictName();
				if(StringUtils.isBlank(dictName)) {
					dictName = field.getName() + DICT_SUFFIX;
				}
				
				String dictValue = String.valueOf(jsonObject.get(field.getName()));
				
				//翻译字典值对应的text值
				Optional<String> textValue = Optional.ofNullable(dictCacheService.getText(dictCode, dictValue));
				//jsonObject.put(dictName, textValue.orElse("未知"));
				
				builder = builder.defineField(dictName, String.class, Modifier.PRIVATE)//.value(value)
					.defineMethod("get" + StringUtils.capitalize(dictName), String.class, Modifier.PUBLIC)
					.intercept(FixedValue.value(textValue.orElse("--")))
				;
				
			}
			
		}
		
		Object returnObject = null;
		try {
			
			/*
			//保存生成的类class文件到某个文件夹
			try {
				builder.make().saveIn(new File("c:/0"));
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			*/
			
			returnObject =  builder.make()
				.load(getClass().getClassLoader())
				//.load(getClass().getClassLoader(), ClassLoadingStrategy.Default.INJECTION)
				.getLoaded()
				.newInstance()
			;
			
		} catch (InstantiationException e) {
			log.error("字典转换出错", e);
			
		} catch (IllegalAccessException e) {
			log.error("字典转换出错", e);
		}
		
		//CglibUtil.copy(data, returnObject);
		
		return returnObject;
		
		//return jsonObject;
		//return data;
	}

defineField：定义字段，即增加字段

defineMethod：定义方法，即增加方法

intercept：拦截defineMethod，设置返回值或者调用的方法

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©Copyright 蕃薯耀 2022-08-31

蕃薯耀的博客_优快云博客-蕃薯耀分享,java,js领域博主