为什么要重构save？
jpa提供的save方法会将原有数据置为null，而大多数情况下我们只希望跟新自己传入的参数，所以便有了重写或者新增一个save方法。
本着解决这个问题，网上搜了很多解决方案，但是没有找到合适的，于是自己研究源码，先展示几个重要源码
1、SimpleJpaRepository方法实现类，由于代码过多只展示部分源码
public class SimpleJpaRepository<T, ID> implements JpaRepository<T, ID>, JpaSpecificationExecutor<T> {
private static final String ID_MUST_NOT_BE_NULL = "The given id must not be null!";
private final JpaEntityInformation<T, ?> entityInformation;
private final EntityManager em;
private final PersistenceProvider provider;
@Nullable
private CrudMethodMetadata metadata;
public SimpleJpaRepository(JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager) {
Assert.notNull(entityInformation, "JpaEntityInformation must not be null!");
Assert.notNull(entityManager, "EntityManager must not be null!");
this.entityInformation = entityInformation;
this.em = entityManager;
this.provider = PersistenceProvider.fromEntityManager(entityManager);
}
public SimpleJpaRepository(Class<T> domainClass, EntityManager em) {
this(JpaEntityInformationSupport.getEntityInformation(domainClass, em), em);
}
public void setRepositoryMethodMetadata(CrudMethodMetadata crudMethodMetadata) {
this.metadata = crudMethodMetadata;
}
@Nullable
protected CrudMethodMetadata getRepositoryMethodMetadata() {
return this.metadata;
}
protected Class<T> getDomainClass() {
return this.entityInformation.getJavaType();
}
private String getDeleteAllQueryString() {
return QueryUtils.getQueryString("delete from %s x", this.entityInformation.getEntityName());
}
@Transactional
public <S extends T> S save(S entity) {
if (this.entityInformation.isNew(entity)) {
this.em.persist(entity);
return entity;
} else {
return this.em.merge(entity);
}
}
}
2、JpaRepositoryFactoryBean
public class JpaRepositoryFactoryBean<T extends Repository<S, ID>, S, ID> extends TransactionalRepositoryFactoryBeanSupport<T, S, ID> {
@Nullable
private EntityManager entityManager;
public JpaRepositoryFactoryBean(Class<? extends T> repositoryInterface) {
super(repositoryInterface);
}
@PersistenceContext
public void setEntityManager(EntityManager entityManager) {
this.entityManager = entityManager;
}
public void setMappingContext(MappingContext<?, ?> mappingContext) {
super.setMappingContext(mappingContext);
}
protected RepositoryFactorySupport doCreateRepositoryFactory() {
Assert.state(this.entityManager != null, "EntityManager must not be null!");
return this.createRepositoryFactory(this.entityManager);
}
protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) {
return new JpaRepositoryFactory(entityManager);
}
public void afterPropertiesSet() {
Assert.state(this.entityManager != null, "EntityManager must not be null!");
super.afterPropertiesSet();
}
}
根据源码及网上资料总结如下方案
一、重写save
优势：侵入性小，缺点将原方法覆盖。
创建JpaRepositoryReBuild方法继承SimpleJpaRepository。直接上代码
public class JpaRepositoryReBuild<T, ID> extends SimpleJpaRepository<T, ID> {
private final JpaEntityInformation<T, ?> entityInformation;
private final EntityManager em;
@Autowired
public JpaRepositoryReBuild(JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager) {
super(entityInformation, entityManager);
this.entityInformation = entityInformation;
this.em = entityManager;
}
/**
* 通用save方法 ：新增/选择性更新
*/
@Override
@Transactional
public <S extends T> S save(S entity) {
//获取ID
ID entityId = (ID) this.entityInformation.getId(entity);
T managedEntity;
T mergedEntity;
if(entityId == null){
em.persist(entity);
mergedEntity = entity;
}else{
managedEntity = this.findById(entityId).get();
if (managedEntity == null) {
em.persist(entity);
mergedEntity = entity;
} else {
BeanUtils.copyProperties(entity, managedEntity, getNullProperties(entity));
em.merge(managedEntity);
mergedEntity = managedEntity;
}
}
return entity;
}
/**
* 获取对象的空属性
*/
private static String[] getNullProperties(Object src) {
//1.获取Bean
BeanWrapper srcBean = new BeanWrapperImpl(src);
//2.获取Bean的属性描述
PropertyDescriptor[] pds = srcBean.getPropertyDescriptors();
//3.获取Bean的空属性
Set<String> properties = new HashSet<>();
for (PropertyDescriptor propertyDescriptor : pds) {
String propertyName = propertyDescriptor.getName();
Object propertyValue = srcBean.getPropertyValue(propertyName);
if (StringUtils.isEmpty(propertyValue)) {
srcBean.setPropertyValue(propertyName, null);
properties.add(propertyName);
}
}
return properties.toArray(new String[0]);
}
}
启动类加上JpaRepositoryReBuild 方法
@EnableJpaRepositories(value = "com.XXX", repositoryBaseClass = JpaRepositoryReBuild.class)
@SpringBootApplication
@EnableDiscoveryClient // 即消费也注册
public class SystemApplication {
public static void main(String[] args) {
SpringApplication.run(SystemApplication.class, args);
}
}
二、扩张jpa方法
1、新建新增方法接口BaseRepository
@NoRepositoryBean
public interface BaseRepository<T, ID extends Serializable> extends JpaRepository<T, ID> {
/**
* 保存但不覆盖原有数据
* @param entity
* @return
*/
T saveNotNull(T entity);
}
2、创建BaseRepositoryImpl方法
@NoRepositoryBean
public class BaseRepositoryImpl<T, ID extends Serializable> extends SimpleJpaRepository<T, ID> implements BaseRepository<T, ID> {
private final JpaEntityInformation<T, ?> entityInformation;
private final EntityManager em;
public BaseRepositoryImpl(JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager) {
super(entityInformation,entityManager);
this.entityInformation = entityInformation;
this.em = entityManager;
}
public BaseRepositoryImpl(Class<T> domainClass, EntityManager em) {
this(JpaEntityInformationSupport.getEntityInformation(domainClass, em), em);
}
@Override
@Transactional
public T saveNotNull(T entity) {
//获取ID
ID entityId = (ID) this.entityInformation.getId(entity);
T managedEntity;
T mergedEntity;
if(entityId == null){
em.persist(entity);
mergedEntity = entity;
}else{
managedEntity = this.findById(entityId).get();
if (managedEntity == null) {
em.persist(entity);
mergedEntity = entity;
} else {
BeanUtils.copyProperties(entity, managedEntity, getNullProperties(entity));
em.merge(managedEntity);
mergedEntity = managedEntity;
}
}
return mergedEntity;
}
private static String[] getNullProperties(Object src) {
//1.获取Bean
BeanWrapper srcBean = new BeanWrapperImpl(src);
//2.获取Bean的属性描述
PropertyDescriptor[] pds = srcBean.getPropertyDescriptors();
//3.获取Bean的空属性
Set<String> properties = new HashSet<>();
for (PropertyDescriptor propertyDescriptor : pds) {
String propertyName = propertyDescriptor.getName();
Object propertyValue = srcBean.getPropertyValue(propertyName);
if (StringUtils.isEmpty(propertyValue)) {
srcBean.setPropertyValue(propertyName, null);
properties.add(propertyName);
}
}
return properties.toArray(new String[0]);
}
}
3、创建工厂BaseRepositoryFactory
public class BaseRepositoryFactory<R extends JpaRepository<T, ID>, T, ID extends Serializable> extends JpaRepositoryFactoryBean<R, T, ID> {
public BaseRepositoryFactory(Class<? extends R> repositoryInterface) {
super(repositoryInterface);
}
@Override
protected RepositoryFactorySupport createRepositoryFactory(EntityManager em) {
return new MyRepositoryFactory(em);
}
private static class MyRepositoryFactory extends JpaRepositoryFactory {
private final EntityManager em;
public MyRepositoryFactory(EntityManager em) {
super(em);
this.em = em;
}
@Override
protected Object getTargetRepository(RepositoryInformation information) {
return new BaseRepositoryImpl((Class) information.getDomainType(), em);
}
@Override
protected Class getRepositoryBaseClass(RepositoryMetadata metadata) {
return BaseRepositoryImpl.class;
}
}
}
4、启动类引入
@EnableJpaRepositories(repositoryFactoryBeanClass = BaseRepositoryFactory.class, basePackages ="com.XXX")
@SpringBootApplication
@EnableDiscoveryClient // 即消费也注册
public class SystemApplication {
public static void main(String[] args) {
SpringApplication.run(SystemApplication.class, args);
}
}