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java怎么复制非空对象属性值

发表于：2025-01-16 作者：千家信息网编辑

千家信息网最后更新 2025年01月16日，小编给大家分享一下java怎么复制非空对象属性值，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！java 复制非空对象属性值很多时候，我们需要通过对象拷贝，比如说VO类与数据库实体be

千家信息网最后更新 2025年01月16日java怎么复制非空对象属性值

小编给大家分享一下java怎么复制非空对象属性值，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！

java 复制非空对象属性值

很多时候，我们需要通过对象拷贝，比如说VO类与数据库实体bean类、更新时非空对象不更新，对同一对象不同数据分开存储等

用于对象拷贝，spring 和 Apache都提供了相应的工具类方法，BeanUtils.copyProperties

但是对于非空属性拷贝就需要自己处理了

在这里借用spring中org.springframework.beans.BeanUtils类提供的方法

copyProperties(Object source, Object target, String... ignoreProperties)

/**     * Copy the property values of the given source bean into the given target bean,     * ignoring the given "ignoreProperties".     * Note: The source and target classes do not have to match or even be derived     * from each other, as long as the properties match. Any bean properties that the     * source bean exposes but the target bean does not will silently be ignored.     * 
This is just a convenience method. For more complex transfer needs,     * consider using a full BeanWrapper.     * @param source the source bean     * @param target the target bean     * @param ignoreProperties array of property names to ignore     * @throws BeansException if the copying failed     * @see BeanWrapper     */    public static void copyProperties(Object source, Object target, String... ignoreProperties) throws BeansException {        copyProperties(source, target, null, ignoreProperties); /**     * Copy the property values of the given source bean into the given target bean.     * 
Note: The source and target classes do not have to match or even be derived     * from each other, as long as the properties match. Any bean properties that the     * source bean exposes but the target bean does not will silently be ignored.     * @param source the source bean     * @param target the target bean     * @param editable the class (or interface) to restrict property setting to     * @param ignoreProperties array of property names to ignore     * @throws BeansException if the copying failed     * @see BeanWrapper     */    private static void copyProperties(Object source, Object target, Class editable, String... ignoreProperties)            throws BeansException {         Assert.notNull(source, "Source must not be null");        Assert.notNull(target, "Target must not be null");         Class actualEditable = target.getClass();        if (editable != null) {            if (!editable.isInstance(target)) {                throw new IllegalArgumentException("Target class [" + target.getClass().getName() +                        "] not assignable to Editable class [" + editable.getName() + "]");            }            actualEditable = editable;        }        PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);        List ignoreList = (ignoreProperties != null ? Arrays.asList(ignoreProperties) : null);         for (PropertyDescriptor targetPd : targetPds) {            Method writeMethod = targetPd.getWriteMethod();            if (writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {                PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());                if (sourcePd != null) {                    Method readMethod = sourcePd.getReadMethod();                    if (readMethod != null &&                            ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {                        try {                            if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {                                readMethod.setAccessible(true);                            }                            Object value = readMethod.invoke(source);                            if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {                                writeMethod.setAccessible(true);                            }                            writeMethod.invoke(target, value);                        }                        catch (Throwable ex) {                            throw new FatalBeanException(                                    "Could not copy property '" + targetPd.getName() + "' from source to target", ex);                        }                    }                }            }        }    }

然后封装一下得到以下方法

/**     * @author zml2015     * @Email zhengmingliang911@gmail.com     * @Time 2017年2月14日 下午5:14:25     * @Description 获取到对象中属性为null的属性名  
     * @param source 要拷贝的对象     * @return     */    public static String[] getNullPropertyNames(Object source) {        final BeanWrapper src = new BeanWrapperImpl(source);        java.beans.PropertyDescriptor[] pds = src.getPropertyDescriptors();         Set emptyNames = new HashSet();        for (java.beans.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);    }     /**     * @author zml2015     * @Email zhengmingliang911@gmail.com     * @Time 2017年2月14日 下午5:15:30     * @Description  拷贝非空对象属性值 
     * @param source 源对象     * @param target 目标对象     */    public static void copyPropertiesIgnoreNull(Object source, Object target) {        BeanUtils.copyProperties(source, target, getNullPropertyNames(source));    }

测试方法就不提供了，自行测试即可

如果项目中使用的框架有Hibernate的话，则可以通过在实体类上添加下面两条注解

@DynamicInsert(true)@DynamicUpdate(true)

如果想对该注解进一步了解的话，那么可以去官网看英文文档，文档解释的很清楚，在此不再赘述了

java对象属性复制的几种方式

1.使用java反射机制

获取对象的属性和get、set方法进行复制；

2.使用spring-beans5.0.8包中的BeanUtils类

import org.springframework.beans.BeanUtils;SourceObject sourceObject = new SourceObject();TargetObject targetObject = new TargetObject();BeanUtils.copyProperties(sourceObject, targetObject);

3.使用cglib3.2.8包中的net.sf.cglib.beans.BeanCopier类

import net.sf.cglib.beans.BeanCopier;import net.sf.cglib.core.Converter;SourceObject sourceObject = new SourceObject();TargetObject targetObject = new TargetObject();BeanCopier beanCopier = BeanCopier.create(SourceObject.class, TargetObject.class, true);--第三个参数表示是否使用转换器，false表示不使用，true表示使用Converter converter = new CopyConverter();--自定义转换器beanCopier.copy(sourceObject, targetObject, converter);

转换器(当源对象属性类型与目标对象属性类型不一致时，使用转换器)：

import net.sf.cglib.core.Converter;import org.apache.commons.lang3.StringUtils;import java.math.BigDecimal;import java.util.Date;/** * Created by asus on 2019/7/12. */public class CopyConverter implements Converter {    @Override    public Object convert(Object value, Class target, Object context) {        {            String s = value.toString();            if (target.equals(int.class) || target.equals(Integer.class)) {                return Integer.parseInt(s);            }            if (target.equals(long.class) || target.equals(Long.class)) {                return Long.parseLong(s);            }            if (target.equals(float.class) || target.equals(Float.class)) {                return Float.parseFloat(s);            }            if (target.equals(double.class) || target.equals(Double.class)) {                return Double.parseDouble(s);            }            if(target.equals(Date.class)){                while(s.indexOf("-")>0){                    s = s.replace("-", "/");                }                return  new Date(s);            }            if(target.equals(BigDecimal.class)){                if(!StringUtils.isEmpty(s)&&!s.equals("NaN")){                    return  new BigDecimal(s);                }            }            return value ;        }    }}

4.使用spring-core5.0.8包

中的org.springframework.cglib.beans.BeanCopier类（用法与第三种一样）

import org.springframework.cglib.beans.BeanCopier;import org.springframework.cglib.core.Converter;SourceObject sourceObject = new SourceObject();TargetObject targetObject = new TargetObject();Converter converter = new SpringCopyConverter();BeanCopier beanCopier = BeanCopier.create(SourceObject.class, TargetObject.class, true);beanCopier.copy(sourceObject, targetObject, converter);

经过循环复制测试(源对象与目标对象各160个属性)：