Spring JPA：在同一查询界面上使用多个投影 [英] Spring JPA: Using multiple projection on same query interface

问题描述

我正在尝试使用Spring JPA的投影从查询结果中过滤掉不必要的数据。但是，我有多个投影需要在同一个接口方法上使用。

I am trying to use Spring JPA's projection to filter out unnecessary data from query result. However, I have multiple projections that will need to be used on the same interface method.

问题是，我试图用不同的方法从同一个方法查询数据返回对象，但java不允许这样做。

The problem is, I am trying to query data from the same method with a different returning object but java doesn't allowed this.

JPA根据方法名称自动生成查询，因此我无法更改方法名称。

The query are auto generated by JPA based on method name, so I cannot make changes to method name.

除了创建新界面之外，还有其他选择吗，因为我认为这是一个麻烦且不必要的

Is there a alternative, other than creating a new interface, since I think it's a hassle and unnecessary

这里有一个示例代码，我想做的。

here is a sample code, of what I am trying to do.

自动生成查询

Auto-Generated Query

public interface UserRepository extends CrudRepository<UserAccount, Long> {

    AuthenticateProjection getByUsername(String username);

    UserDetailsProjection getByUsername(String username);

}

预测

Projections

public interface AuthenticateProjection {

    @Value("#{target.username}")
    String getUsername();

    @Value("#{target.credentail.token}")
    String getHashPassword();
}

public interface UserDetailsProjection {

    @Value("#{target.username}")
    String getUsername();

    @Value("#{target.firstname}")
    String getFirstName();

    @Value("#{target.lastname}")
    String getLastName();
}

推荐答案

所以我成功了弄清楚如何使用单个查询使用多个投影。

So I've managed to figure out how to use multiple projections with a single query.

<T> T getByUsername(String username, Class<T> projection)

这允许方法调用者指定类型要应用于查询的投影。

This allows the method caller to specified the type of projection to be applied to the query.

为了进一步改进这一点，它不容易出错，我做了一个空白界面，投影必须按顺序扩展能够将类插入参数。

To further improve this so it is less prone to error, I made a blank interface that the projection will have to extend in order to be able to insert class into the parameter.

public interface JPAProjection {
}

public interface UserRepository extends CrudRepository<UserAccount, Long> {
    <T extends JPAProjection > T getByUsername(String username, Class<? extends JPAProjection> projection);
}

投影界面

Projection Interface

public interface UserDetailsProjection extends JPAProjection{
    @Value("#{target.username}")
    String getUsername();

    @Value("#{target.firstname}")
    String getFirstname();

    @Value("#{target.lastname}")
    String getLastname();
}

然后我可以通过

getByUsername("...", UserDetailsProjection.class)

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