BeanUtils.copyProperties忽略null值

可以使用BeanMapper或者在BeanUtils.copyProperties中传入一个自定义的属性过滤器来忽略null值。以下是两种方法的示例代码：

1. 使用BeanMapper忽略null值

import net.sf.cglib.beans.BeanCopier;
import net.sf.cglib.core.Converter;

public class BeanMapper {
    private static final Map<String, BeanCopier> BEAN_COPIERS = new ConcurrentHashMap<>();

    public static void copyProperties(Object source, Object target) {
        String key = source.getClass().toString() + target.getClass().toString();
        BeanCopier copier = null;
        if (!BEAN_COPIERS.containsKey(key)) {
            copier = BeanCopier.create(source.getClass(), target.getClass(), true);
            BEAN_COPIERS.put(key, copier);
        } else {
            copier = BEAN_COPIERS.get(key);
        }
        copier.copy(source, target, new Converter() {
            @Override
            public Object convert(Object value, Class target, Object context) {
                if (value == null) {
                    if (target == String.class) {
                        return "";
                    } else if (target == Integer.class) {
                        return 0;
                    } else if (target == Long.class) {
                        return 0L;
                    } else if (target == Double.class) {
                        return 0.0;
                    } else if (target == Float.class) {
                        return 0.0f;
                    } else if (target == Boolean.class) {
                        return false;
                    } else {
                        return null;
                    }
                } else {
                    return value;
                }
            }
        });
    }
}

使用示例：

Source source = new Source();
source.setName("test");
source.setAge(18);
source.setAddress(null);

Target target = new Target();
BeanMapper.copyProperties(source, target);

System.out.println(target.getName()); // 输出：test
System.out.println(target.getAge()); // 输出：18
System.out.println(target.getAddress()); // 输出：null

2. 在BeanUtils.copyProperties中传入自定义属性过滤器忽略null值

import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;

import java.beans.PropertyDescriptor;
import java.util.HashSet;
import java.util.Set;

public class CopyUtils {
    public static void copyPropertiesIgnoreNull(Object source, Object target) {
        BeanUtils.copyProperties(source, target, getNullPropertyNames(source));
    }

    private static String[] getNullPropertyNames(Object source) {
        final BeanWrapper src = new BeanWrapperImpl(source);
        PropertyDescriptor[] pds = src.getPropertyDescriptors();

        Set<String> emptyNames = new HashSet<>();
        for (PropertyDescriptor pd : pds) {
            Object srcValue = src.getPropertyValue(pd.getName());
            if (srcValue == null) {
                emptyNames.add(pd.getName());
            }
        }
        String[] result = new String[emptyNames.size()];
        return emptyNames.toArray(result);
    }
}

使用示例：

Source source = new Source();
source.setName("test");
source.setAge(18);
source.setAddress(null);

Target target = new Target();
CopyUtils.copyPropertiesIgnoreNull(source, target);

System.out.println(target.getName()); // 输出：test
System.out.println(target.getAge()); // 输出：18
System.out.println(target.getAddress()); // 输出：null