1. 反射
使用了缺省的方式进行copy。要求源对象和目标对象必须实现getter和setter。进行copy时，内部会缓存缺省对象，以优化性能。
源码位置：org.springframework.beans.BeanUtils
public class TestJavaUtils {
public static void main(String[] args) {
UserPo userPo=new UserPo();
userPo.setId(1001L);
userPo.setName("tom");
userPo.setAge(12);
UserDto userDto=new UserDto();
//源对象：目标对象
BeanUtils.copyProperties(userPo,userDto);
System.out.println(userDto);
}
@Data
public static class UserDto{
private Long id;
private String name;
private Integer age;
private String sex;
}
@Data
public static class UserPo{
private Long id;
private String name;
private Integer age;
}
}
2. cglib字节码
copy对象时，可以使用CGLib的BeanCopier（其原理是运行时动态生成了用于复制某个类的字节码），其性能比反射框架org.springframework.beans.BeanUtils性能要高。
/**
* @param source 原始对象
* @param targetClass 拷贝的对象类型
*/
public static < T1,T2 > T2 createCopy(T1 source, Class < T2 > targetClass) {
if (source == null) {
throw new RuntimeException("参数异常");
} else {
T2 target;
try {
target = targetClass.newInstance();
} catch(Exception e) {
throw new RuntimeException(e);
}
BeanCopier beanCopier = BeanCopier.create(source.getClass(), targetClass, false);
beanCopier.copy(source, target, null);
return target;
}
}
缓存优化版
private static Map<String, BeanCopier> beanCopierMap = new ConcurrentHashMap();
/**
* 拷贝对象.
* 只能拷贝 字段名&类型&getter类型完全一致的属性。
* 但是Long->long int->long 是无法拷贝的。
* <p>
* 效率：该方法的效率是 Spring.BeanUtil.copy的100倍以上。基本和系统的set是等效率的，某些场景下甚至比set还快
*
* @param dest 目标对象
* @param source 源对象
*/
public static void copyBean(Object dest, Object source) {
//缓存的key
String key = generateKey(source.getClass(), dest.getClass());
try {
BeanCopier beanCopier = beanCopierMap.get(key);
//此处可以避免computeIfAbsent性能问题。
if (beanCopier == null) {
beanCopier = beanCopierMap.computeIfAbsent(key,
k -> BeanCopier.create(source.getClass(), dest.getClass(), false));
}
beanCopier.copy(source, dest, null);
} catch (Throwable e) {
log.error("", e);
}
}
3. get和set的链式拷贝
本质是使用getter和setter的方式进行copy，但是借助了jdk8的链式编程。
org.springframework.amqp.utils.JavaUtils源码位置（未引入rabbitMq可以粘贴代码到项目里面）：
源码中使用如下方式进行copy的。
public final class JavaUtils {
/**
* The singleton instance of this utility class.
*/
public static final JavaUtils INSTANCE = new JavaUtils();
private JavaUtils() {
super();
}
/**
* Invoke {@link Consumer#accept(Object)} with the value if the condition is true.
* @param condition the condition.
* @param value the value.
* @param consumer the consumer.
* @param <T> the value type.
* @return this.
*/
public <T> JavaUtils acceptIfCondition(boolean condition, T value, Consumer<T> consumer) {
if (condition) {
consumer.accept(value);
}
return this;
}
/**
* Invoke {@link Consumer#accept(Object)} with the value if it is not null.
* @param value the value.
* @param consumer the consumer.
* @param <T> the value type.
* @return this.
*/
public <T> JavaUtils acceptIfNotNull(T value, Consumer<T> consumer) {
if (value != null) {
consumer.accept(value);
}
return this;
}
/**
* Invoke {@link Consumer#accept(Object)} with the value if it is not null or empty.
* @param value the value.
* @param consumer the consumer.
* @return this.
*/
public JavaUtils acceptIfHasText(String value, Consumer<String> consumer) {
if (StringUtils.hasText(value)) {
consumer.accept(value);
}
return this;
}
/**
* Invoke {@link BiConsumer#accept(Object, Object)} with the arguments if the
* condition is true.
* @param condition the condition.
* @param t1 the first consumer argument
* @param t2 the second consumer argument
* @param consumer the consumer.
* @param <T1> the first argument type.
* @param <T2> the second argument type.
* @return this.
*/
public <T1, T2> JavaUtils acceptIfCondition(boolean condition, T1 t1, T2 t2, BiConsumer<T1, T2> consumer) {
if (condition) {
consumer.accept(t1, t2);
}
return this;
}
/**
* Invoke {@link BiConsumer#accept(Object, Object)} with the arguments if the t2
* argument is not null.
* @param t1 the first argument
* @param t2 the second consumer argument
* @param consumer the consumer.
* @param <T1> the first argument type.
* @param <T2> the second argument type.
* @return this.
*/
public <T1, T2> JavaUtils acceptIfNotNull(T1 t1, T2 t2, BiConsumer<T1, T2> consumer) {
if (t2 != null) {
consumer.accept(t1, t2);
}
return this;
}
/**
* Invoke {@link BiConsumer#accept(Object, Object)} with the arguments if the value
* argument is not null or empty.
* @param t1 the first consumer argument.
* @param value the second consumer argument
* @param <T> the first argument type.
* @param consumer the consumer.
* @return this.
*/
public <T> JavaUtils acceptIfHasText(T t1, String value, BiConsumer<T, String> consumer) {
if (StringUtils.hasText(value)) {
consumer.accept(t1, value);
}
return this;
}
}
测试用例：
public class TestJavaUtils {
/**
* 对象的copy链式。
*/
public static void main(String[] args) {
UserPo userPo=new UserPo();
userPo.setId(1001L);
userPo.setName("tom");
userPo.setAge(12);
UserDto userDto=new UserDto();
JavaUtils.INSTANCE.acceptIfNotNull(userPo.getAge(),userDto::setAge).acceptIfNotNull(userPo.getName(),userDto::setName);
System.out.println(userDto);
}
@Data
public static class UserDto{
private Long id;
private String name;
private Integer age;
private String sex;
}
@Data
public static class UserPo{
private Long id;
private String name;
private Integer age;
}
}
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