java动态给实体类添加属性

 

需要的jar包有两个： cglib-3.1.jar 和 google-collections-1.0.jar 
如果是maven项目，就不需要cglib-3.1.jar，直接用spring自带的 org.springframework.cglib即可。 
1、创建一个实体：DynamicBean

public class DynamicBean {

    private Object target;
    private BeanMap beanMap;

    public DynamicBean(Class superclass, Map<String, Class> propertyMap) {
        this.target = generateBean(superclass, propertyMap);
        this.beanMap = BeanMap.create(this.target);
    }

    public void setValue(String property, Object value) {
        beanMap.put(property, value);
    }

    public Object getValue(String property) {
        return beanMap.get(property);
    }

    public Object getTarget() {
        return this.target;
    }
    /**
     * 根据属性生成对象
     *
     */
    private Object generateBean(Class superclass, Map<String, Class> propertyMap) {
        BeanGenerator generator = new BeanGenerator();
        if (null != superclass) {
            generator.setSuperclass(superclass);
        }
        BeanGenerator.addProperties(generator, propertyMap);
        return generator.create();
    }
}

2、创建映射类，用来生成动态bean

public class ReflectUtil {
	private static Logger logger = LoggerFactory.getLogger(ReflectUtil.class);
	
	public static Object getObject(Object dest, Map<String, Object> addProperties) {
	    PropertyUtilsBean propertyUtilsBean = new PropertyUtilsBean();
	    PropertyDescriptor[] descriptors = propertyUtilsBean.getPropertyDescriptors(dest);
	    Map<String, Class> propertyMap = Maps.newHashMap();
	    for (PropertyDescriptor d : descriptors) {
	        if (!"class".equalsIgnoreCase(d.getName())) {
	            propertyMap.put(d.getName(), d.getPropertyType());
	        }
	    }
	    addProperties.forEach((k, v) -> {
	    	String sclass = v.getClass().toString();
	    	if(sclass.equals("class java.util.Date")) {//对日期进行处理
	    		propertyMap.put(k, Long.class);
	    	}else {
	    		propertyMap.put(k, v.getClass());
	    	}
	    	
	    });
	    DynamicBean dynamicBean = new DynamicBean(dest.getClass(), propertyMap);
	    propertyMap.forEach((k, v) -> {
	        try {
	            if (!addProperties.containsKey(k)) {
	                dynamicBean.setValue(k, propertyUtilsBean.getNestedProperty(dest, k));
	            }
	        } catch (Exception e) {
	            logger.error("动态添加字段出错", e);
	        }
	    });
	    addProperties.forEach((k, v) -> {
	        try {
	        	String sclass = v.getClass().toString();
		    	if(sclass.equals("class java.util.Date")) {//动态添加的字段为date类型需要进行处理
		    		Date date = (Date) v;
		    		dynamicBean.setValue(k, date.getTime());
		    	}else {
		    		dynamicBean.setValue(k, v);
		    	}
	        } catch (Exception e) {
	        	logger.error("动态添加字段值出错", e);
	        }
	    });
	    Object obj = dynamicBean.getTarget();
	    return obj;
	}
}

3、使用方法
现有一个用户实体User：

public class User {

	private String name;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	
}

User只有一个name属性，现在要动态的为User添加年龄属性，代码如下：

public static void main(String[] args) {
		User user = new User();
		user.setName("Daisy");
		System.out.println("User："+JSON.toJSONString(user));
		Map<String,Object> propertiesMap = new HashMap<String,Object>();
		propertiesMap.put("age", 18);
		Object obj = ReflectUtil.getTarget(user, propertiesMap);
		System.out.println("动态为User添加age之后，User："+JSON.toJSONString(obj));
}

 

打印结果如下：

User：{"name":"Daisy"}
动态为User添加age之后，User：{"age":18,"name":"Daisy"}