使用CGlib实现Bean拷贝(BeanCopier)
在做业务的时候，我们有时为了隔离变化，会将DAO查询出来的Entity，和对外提供的DTO隔离开来。大概90%的时候，它们的结构都是类似的，但是我们很不喜欢写很多冗长的b.setF1(a.getF1())这样的代码，于是我们需要BeanCopier来帮助我们。选择Cglib的BeanCopier进行Bean拷贝的理由是，其性能要比Spring的BeanUtils，Apache的BeanUtils和PropertyUtils要好很多，尤其是数据量比较大的情况下。
BeanCopier基本用法
public class User {
private int age;
private String name;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public class UserDto {
private int age;
private String name;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public class UserWithDiffType {
private Integer age;
private String name;
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
1. 属性名称、类型都相同:
@Test
public void normalCopyTest() {
// create(Class source, Class target, boolean useConverter)
final BeanCopier beanCopier = BeanCopier.create(User.class, UserDto.class, false);
User user = new User();
user.setAge(10);
user.setName("zhangsan");
UserDto userDto = new UserDto();
beanCopier.copy(user, userDto, null);
Assert.assertEquals(10, userDto.getAge());
Assert.assertEquals("zhangsan", userDto.getName());
}
结论：属性名称相同类型相同的属性拷贝OK。
2. 属性名称相同、类型不同：
@Test
public void normalCopyTest() {
// create(Class source, Class target, boolean useConverter)
final BeanCopier beanCopier = BeanCopier.create(User.class, UserWithDiffType.class, false);
User user = new User();
user.setAge(10);
user.setName("zhangsan");
UserWithDiffType userDto = new UserWithDiffType();
beanCopier.copy(user, userDto, null);
Assert.assertEquals(null, userDto.getAge());
Assert.assertEquals("zhangsan", userDto.getName());
}
结论：属性名称相同而类型不同的属性不会被拷贝。
注意：即使源类型是原始类型(int, short和char等)，目标类型是其包装类型(Integer, Short和Character等)，或反之：都 不会被拷贝。
总结：
BeanCopier只拷贝名称和类型都相同的属性。
自定义转换器
当源和目标类的属性类型不同时，不能拷贝该属性，此时我们可以通过实现Converter接口来自定义转换器
源类和目标类：
public class Account {
private int id;
private Date createTime;
private BigDecimal balance;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Date getCreateTime() {
return createTime;
}
public void setCreateTime(Date createTime) {
this.createTime = createTime;
}
public BigDecimal getBalance() {
return balance;
}
public void setBalance(BigDecimal balance) {
this.balance = balance;
}
}
public class AccountDto {
private int id;
private String createTime;
private String balance;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCreateTime() {
return createTime;
}
public void setCreateTime(String createTime) {
this.createTime = createTime;
}
public String getBalance() {
return balance;
}
public void setBalance(String balance) {
this.balance = balance;
}
}
1. 不使用Converter
@Test
public void noConverterTest() {
Account po = new Account();
po.setId(1);
po.setCreateTime(new Date());
po.setBalance(BigDecimal.valueOf(4000L));
BeanCopier copier = BeanCopier.create(Account.class, AccountDto.class, false);
AccountDto dto = new AccountDto();
copier.copy(po, dto, null);
// 类型不同，未拷贝
Assert.assertNull(dto.getBalance());
// 类型不同，未拷贝
Assert.assertNull(dto.getCreateTime());
}
2. 使用Converter
基于目标对象的属性出发，如果源对象有相同名称的属性，则调一次convert方法：
public class TestCase {
@Test
public void noConverterTest() {
Account po = new Account();
po.setId(1);
po.setCreateTime(new Date());
po.setBalance(BigDecimal.valueOf(4000L));
BeanCopier copier = BeanCopier.create(Account.class, AccountDto.class, true);
AccountDto dto = new AccountDto();
AccountConverter converter = new AccountConverter();
copier.copy(po, dto, converter);
// 类型不同，未拷贝
Assert.assertEquals("4000", dto.getBalance());
// 类型不同，未拷贝
Assert.assertEquals("2018-12-13", dto.getCreateTime());
}
}
class AccountConverter implements Converter {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
@SuppressWarnings("rawtypes")
@Override
public Object convert(Object source, Class target, Object context) {
if (source instanceof Integer) {
return (Integer) source;
} else if (source instanceof Date) {
Date date = (Date) source;
return sdf.format(date);
} else if (source instanceof BigDecimal) {
BigDecimal bd = (BigDecimal) source;
return bd.toPlainString();
}
return null;
}
}
注：一旦使用Converter，BeanCopier只使用Converter定义的规则去拷贝属性，所以在convert方法中要考虑所有的属性。
封装BeanCopier
@Test
public void costTest() {
List<User> list1 = new ArrayList<>(100);
for (int i = 0; i < 100; i++) {
User po = new User();
po.setId(1);
po.setCreateTime(new Date());
po.setBalance(BigDecimal.valueOf(4000L));
list1.add(po);
}
BeanCopier copier = BeanCopier.create(User.class, UserDto.class, false);
long start = System.currentTimeMillis();
List<UserDto> list2 = new ArrayList<>(100);
for (User user : list1) {
UserDto dto = new UserDto();
//BeanUtils.beanCopy(user, dto);
copier.copy(user, dto, null);
list2.add(dto);
}
System.out.printf("took time: %d(ms)%n",System.currentTimeMillis() - start);
}
经过测试，BeanCopier性能是BeanUtils10倍左右。
BeanCopier拷贝速度快，性能瓶颈出现在创建BeanCopier实例的过程中。 所以，把创建过的BeanCopier实例放到缓存中，下次可以直接获取，提升性能：
依赖：
<dependencies>
<dependency>
<groupId>cglib</groupId>
<artifactId>cglib</artifactId>
<version>3.2.10</version>
</dependency>
<dependency>
<groupId>com.esotericsoftware</groupId>
<artifactId>reflectasm</artifactId>
<version>1.11.7</version>
</dependency>
</dependencies>
封装工具
public class WrapperBeanCopier {
private WrapperBeanCopier() {
//do nothing
}
private static final Map<String, BeanCopier> BEAN_COPIER_CACHE = new ConcurrentHashMap<>();
private static final Map<String, ConstructorAccess> CONSTRUCTOR_ACCESS_CACHE = new ConcurrentHashMap<>();
public static void copyProperties(Object source, Object target) {
BeanCopier copier = getBeanCopier(source.getClass(), target.getClass());
copier.copy(source, target, null);
}
private static BeanCopier getBeanCopier(Class sourceClass, Class targetClass) {
String beanKey = generateKey(sourceClass, targetClass);
BeanCopier copier = null;
if (!BEAN_COPIER_CACHE.containsKey(beanKey)) {
copier = BeanCopier.create(sourceClass, targetClass, false);
BEAN_COPIER_CACHE.put(beanKey, copier);
} else {
copier = BEAN_COPIER_CACHE.get(beanKey);
}
return copier;
}
/**
* 两个类的全限定名拼接起来构成Key
*
* @param sourceClass
* @param targetClass
* @return
*/
private static String generateKey(Class<?> sourceClass, Class<?> targetClass) {
return sourceClass.getName() + targetClass.getName();
}
public static <T> T copyProperties(Object source, Class<T> targetClass) {
T t = null;
try {
t = targetClass.newInstance();
} catch (InstantiationException | IllegalAccessException e) {
throw new RuntimeException(format("Create new instance of %s failed: %s", targetClass, e.getMessage()));
}
copyProperties(source, t);
return t;
}
public static <T> List<T> copyPropertiesOfList(List<?> sourceList, Class<T> targetClass) {
if (sourceList == null || sourceList.isEmpty()) {
return Collections.emptyList();
}
ConstructorAccess<T> constructorAccess = getConstructorAccess(targetClass);
List<T> resultList = new ArrayList<>(sourceList.size());
for (Object o : sourceList) {
T t = null;
try {
t = constructorAccess.newInstance();
copyProperties(o, t);
resultList.add(t);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
return resultList;
}
private static <T> ConstructorAccess<T> getConstructorAccess(Class<T> targetClass) {
ConstructorAccess<T> constructorAccess = CONSTRUCTOR_ACCESS_CACHE.get(targetClass.getName());
if (constructorAccess != null) {
return constructorAccess;
}
try {
constructorAccess = ConstructorAccess.get(targetClass);
constructorAccess.newInstance();
CONSTRUCTOR_ACCESS_CACHE.put(targetClass.toString(), constructorAccess);
} catch (Exception e) {
throw new RuntimeException(format("Create new instance of %s failed: %s", targetClass, e.getMessage()));
}
return constructorAccess;
}
}
标签: 工具类
