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)
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
|
/** * Copy the property values of the given source bean into the given target bean, * ignoring the given "ignoreProperties". * <p>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. * <p>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. * <p>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<String> 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
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
|
/** * @author zml2015 * @Email zhengmingliang911@gmail.com * @Time 2017年2月14日 下午5:14:25 * @Description <p>获取到对象中属性为null的属性名 </P> * @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<String> emptyNames = new HashSet<String>(); 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 <p> 拷贝非空对象属性值 </P> * @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
|
1
2
|
@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
|
1
2
3
4
|
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
|
1
2
3
4
5
6
7
|
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)：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
|
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）
|
1
2
3
4
5
6
7
|
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)：
- 第一种：Java反射通过判断属性类型，常用类型的属性值都能复制，但是不优化的前提下效率最慢；
- 第二种：属性类型不同时无法复制，且效率相对较慢；
- 第三种：耗时最少，不使用转换器时，属性类型不同时无法复制，使用转换器后，耗时会相对变长；
- 第四种：与第三种相似，但是耗时相对较长；
以上为个人经验，希望能给大家一个参考，也希望大家多多支持服务器之家。
原文链接：https://alianga.blog.csdn.net/article/details/55192785
