Java 通过反射给 null值的字段属性批量赋值

素颜马尾好姑娘i 2023-09-24 23:32 70阅读 0赞

工具类：

DefaultValueUtil.java

import com.google.common.collect.Lists;
    import com.google.common.collect.Sets;
    
    import java.lang.reflect.Field;
    import java.lang.reflect.Method;
    import java.lang.reflect.ParameterizedType;
    import java.lang.reflect.Type;
    import java.math.BigDecimal;
    import java.util.*;
    
    
    
    public class DefaultValueUtil {
    
        /**
         * 給为null的字段赋默认值
         *
         * @param obj
         * @return
         */
        private static Object setDefaultValue(Object obj) {
            Field[] fields = obj.getClass().getDeclaredFields();
            Method[] methods = obj.getClass().getDeclaredMethods();
            Map<String, Method> methodNameMethodMap = new HashMap(methods.length);
            for (Method method : methods) {
                methodNameMethodMap.put(method.getName().toLowerCase(), method);
            }
            for (Field field : fields) {
                Class<?> clazz = field.getType();
                String propertyName = field.getName();
                try {
                    String firstLetter = propertyName.substring(0, 1).toUpperCase();
                    String getter = "get" + firstLetter + propertyName.substring(1);
                    Method method0 = obj.getClass().getMethod(getter, new Class[]{});
                    Object value = method0.invoke(obj, new Object[]{});
                    if (value != null) {
                        continue;
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
                Method method = methodNameMethodMap.get("set" + propertyName.toLowerCase());
                if (method == null) {
                    continue;
                }
                try {
                    if (isWrapClass(clazz) || clazz.isPrimitive()) {
                        if (clazz == Boolean.class || clazz.getName().contains("boolean")) {
                            method.invoke(obj, Boolean.FALSE);
                        } else if (clazz == Byte.class || clazz.getName().contains("byte")) {
                            method.invoke(obj, new Byte("0"));
                        } else if (clazz == Short.class || clazz.getName().contains("short")) {
                            method.invoke(obj, new Short("0"));
                        } else if (clazz == Integer.class || clazz.getName().contains("int")) {
                            method.invoke(obj, 0);
                        } else if (clazz == Long.class || clazz.getName().contains("long")) {
                            method.invoke(obj, 0L);
                        } else if (clazz == Float.class || clazz.getName().contains("float")) {
                            method.invoke(obj, 0F);
                        } else if (clazz == Double.class || clazz.getName().contains("double")) {
                            method.invoke(obj, 0D);
                        } else if (clazz == Character.class || clazz.getName().contains("char")) {
                            method.invoke(obj, '0');
                        }
                    } else if (BigDecimal.class.isAssignableFrom(clazz)) {
                        method.invoke(obj, BigDecimal.ZERO);
                    } else if (Date.class.isAssignableFrom(clazz)) {
                        method.invoke(obj, new Date());
                    } else if (String.class.isAssignableFrom(clazz)) {
                        method.invoke(obj, "");
                    } else if (Collection.class.isAssignableFrom(clazz) || Map.class.isAssignableFrom(clazz)) {
                        Type[] type = method.getGenericParameterTypes();
                        ParameterizedType pType = (ParameterizedType) type[0];
                        Collection collection = null;
                        if (pType.getRawType().toString().endsWith("List")) {
                            collection = Lists.newArrayList();
                        } else if (pType.getRawType().toString().endsWith("Set")) {
                            collection = Sets.newHashSet();
                        }
                        Object objValue = null;
                        try {
                            objValue = Class.forName(pType.getActualTypeArguments()[0].getTypeName()).newInstance();
                        } catch (Exception e) {
                        }
                        if (objValue == null) {
                            continue;
                        }
                        Object childObj = setDefaultValue(objValue);
                        collection.add(childObj);
                        method.invoke(obj, collection);
                    } else {
                        method.invoke(obj, setDefaultValue(clazz.newInstance()));
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            return obj;
        }
    
        public static boolean isWrapClass(Class clz) {
            try {
                return ((Class) clz.getField("TYPE").get(null)).isPrimitive();
            } catch (Exception e) {
                return false;
            }
        }
    
        public static void main(String[] args) {
            TestDTO dto = new TestDTO();
            dto.setTAmount(new BigDecimal("999"));
            dto.setRemark("点赞收藏");
            System.out.println("前：" + dto.toString());
            Object o = setDefaultValue(dto);
            System.out.println("后：" + o.toString());
        }
    
    
    }

效果：  
  
![2a1e257c180041c693904463343aed1e.png][]

注意点：  
  
![9ad456841701485f9f5932af25ea72a7.png][]

什么时候需要使用 这种反射赋值的场景， 大家也是需要有取舍有考虑

好了，该篇就到这。

[2a1e257c180041c693904463343aed1e.png]: https://img-blog.csdnimg.cn/2a1e257c180041c693904463343aed1e.png
[9ad456841701485f9f5932af25ea72a7.png]: https://img-blog.csdnimg.cn/9ad456841701485f9f5932af25ea72a7.png