如何使用jpa/spring-boot正确应用PrePersist之类的逻辑 [英] How to properly apply PrePersist like logic using jpa/spring-boot

问题描述

对于以下模型，我有一个非常简单的用例

I have a very simple use case for the following model

@Entity
@Table(name='Foo')
class Foo {
    @Id
    String id = UUID.randomUUID()    
    String bar
    Date foo_updated
}

当我看到传入的json有效负载具有"bar"的值时，我想将foo_updated值设置为new Date()(即-这是POST中包含的新值/PATCH更新的一部分) /包含在内，并证明在PUT中与众不同)

I'd like to set the foo_updated value to new Date() when I see the incoming json payload has a value for "bar" (ie- this is a new value included in the POST/ a part of the PATCH update / included and proven to be different in a PUT)

我希望在此模型上简单地应用@PrePersist批注，并添加一个简单的条件询问"bar"是否有效...但很快意识到我不知道该值是否与其中的值不同"数据库(对于PATCH/PUT场景).

I was hoping to simply apply the @PrePersist annotation on this model and add a simple conditional asking if "bar" was valid ...but quickly realized I wouldn't know if the value was "different" from what was in the db already (for the PATCH/PUT scenario).

我正在开始添加我自己的RestController"，并在使用spring 4 ResponseEntity方法的过程中应用此逻辑，但是...我觉得这可能最终会花费更多的工作/更多的代码保持.

I'm starting down the road of "add my own RestController" and apply this logic on the way in using the spring 4 ResponseEntity approach but ... I feel this might end up being a lot more work/more code to maintain.

当我是spring-boot/spring-mvc/jpa的新手时，我很好奇我还有什么其他选择，并且对于这种看似简单"的要求，首选的方法是什么

As I'm new to spring-boot/spring-mvc/jpa I'm curious what other options I have and what the preferred approach would be for this seemingly "simple" requirement

感谢您的帮助！

推荐答案

我最近遇到了这种方法，该方法涉及记录加载时的先前状态.新值绑定后，您现在可以访问以前的状态.

I came across this approach recently which involves recording the previous state on load. You now have access to the previous state after the new values are bound.

@Entity
@Table(name='Foo')
class Foo {
    @Id
    String id = UUID.randomUUID()    
    String bar
    Date foo_updated

    @Transient
    private Foo previousState;

    @PostLoad
    private void setPreviousState(){
        previousState = new Foo();
        //copy the fields
    }

}

但是，就您而言，您不能这样做:

However in your case can't you just do:

@Entity
@Table(name='Foo')
class Foo {
    @Id
    private String id = UUID.randomUUID()    
    private String bar
    private Date lastUpdated;

    public void setBar(String bar){
        if(! this.bar.equals(bar){
            lastUpdated = new Date();
        }
    }
}

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