详解SpringDataJpa当属性为Null也更新的完美解决方案

@Entity
public class User{

 public User(){

 }

 @Id
 @GeneratedValue
 public Long id;

 private String name;
 private String mobileNo;
 private String email;
 private String password;
 private Integer type;
 private Date registerTime;
 private String region;
 private Integer validity;

 setter...
 getter...
}

@RestController
public class UserController {
 @Autowired
 private UserDao userDao;

 @PostMapping(value = "/save")
 public String save(@RequestBody User u) {
  userDao.save(u)
  return "更新成功";
 }
}

 {
  "id" : "1",
  "name" : "张三"
 }

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;

/**
 * There is no royal road to learning.
 * Description:提交实体对象中的null赋值
 * Created by 贤领·周 on 2018年04月10日 15:26
 */
public class UpdateTool {
 /**
  * 将目标源中不为空的字段过滤，将数据库中查出的数据源复制到提交的目标源中
  *
  * @param source 用id从数据库中查出来的数据源
  * @param target 提交的实体，目标源
  */
 public static void copyNullProperties(Object source, Object target) {
  BeanUtils.copyProperties(source, target, getNoNullProperties(target));
 }

 /**
  * @param target 目标源数据
  * @return 将目标源中不为空的字段取出
  */
 private static String[] getNoNullProperties(Object target) {
  BeanWrapper srcBean = new BeanWrapperImpl(target);
  PropertyDescriptor[] pds = srcBean.getPropertyDescriptors();
  Set noEmptyName = new HashSet<>();
  for (PropertyDescriptor p : pds) {
   Object value = srcBean.getPropertyValue(p.getName());
   if (value != null) noEmptyName.add(p.getName());
  }
  String[] result = new String[noEmptyName.size()];
  return noEmptyName.toArray(result);
 }
}

 /**
  * 通过源码不难看出，该方法就是将source的属性值复制到target中
  * 
  * @param source 数据源（也就是我们通过id去数据库查询出来的数据）
  * @param target 目标源（也就是我们请求更新的数据）
  * @param ignoreProperties (需要过滤的字段)
  */
 public static void copyProperties(Object source, Object target, String... ignoreProperties) throws BeansException {
  copyProperties(source, target, (Class)null, ignoreProperties);
 }


 private static void copyProperties(Object source, Object target, Class<&＃63;> editable, String... ignoreProperties) throws BeansException {
  Assert.notNull(source, "Source must not be null");
  Assert.notNull(target, "Target must not be null");
  Class<&＃63;> 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 &＃63; Arrays.asList(ignoreProperties) : null;
  PropertyDescriptor[] var7 = targetPds;
  int var8 = targetPds.length;

  for(int var9 = 0; var9 

@RestController
public class UserController {
 @Autowired
 private UserDao userDao;

 @PostMapping(value = "/save")
 public String save(@RequestBody User u) {
  if(u.getId != 0){
   User source= userDao.findOne(u.getId);
   UpdateTool.copyNullProperties(source, u);
  }
  userDao.save(u)
  return "更新成功";
 }
}

 {
  "id" : "1",
  "name" : "张三"
 }