当查询存储为外部文件时，如何在 Spring boot Repository 中为本机查询填充 @Query 值

Question

Similar question has been asked and answered back in 2015 here .

However , rather than storing queries in XML files , I would like to store them in external .sql files and read query from there. To achieve this in our spring boot application - 2.1.5.RELEASE with Java 8 , we are storing queries in resources folder as below

src/main/resources - queries - A.sql - B.sql

To read the above queries , I'm reading them in QueryReader class as below

@Component
public class QueryReader {

    public String getQueryFromFile(String fileName) {
        System.out.println("getQueryFromFile() : " + fileName);
        return this.convertInputStreamToString(this.getTemplateAsStream(fileName));
    }




     private InputStream getTemplateAsStream(String queryFileName){
            ClassLoader classLoader = getClass().getClassLoader();
            InputStream iStream =classLoader.getResourceAsStream("queries/" + queryFileName);

            return iStream;
        }
}

And to use it anywhere in the code , i'm having below class , so that i can call it's methods

@Component
public class MyQueries {


    @Autowired
    private QueryReader qfr;

    public String queryErroredRecords() {
        return qfr.getQueryFromFile("A.sql");
    }

While using it with JDBCTemplate , this works as expected but when I'm trying to use this method from @Query annotation from Repository , i'm not able to do so with errors as below.

Repository Code

@Repository
public interface AdminRepository extends JpaRepository<OrderBackupRecordEO, BigDecimal>{

    @Autowired
    public MyQueries queries;


@Query(value = queries.queryErroredRecords() , nativeQuery= true)
    List<String> findX();
}

Above repository is giving errors as below :

1.The value for annotation attribute Query.value must be a constant expression (For @Query annotation)

2.The blank final field queries may not have been initialized (For @Autowired annotation)

How can I make it work?

Answer 1

I would just add a note that may be helpful for you.

Your solution cannot work just because in java in an interface all the fields (variables) are by default public , static and final and that why you cannot @Autowire any dependencies inside the interface.

That's why it works for your case for JDBCTemplate (which is a class) and doesn't work for spring data repository (which is an interface).

Answer 2

Spring already has a solution "from the box", you don't need to make all these manipulations.

@Repository
public interface AdminRepository extends JpaRepository<OrderBackupRecordEO, BigDecimal> {

    List<String> findX();
}

File src/main/resources/META-INF/jpa-named-queries.properties :

OrderBackupRecordEO.findX=\
    SELECT record FROM OrderBackupRecordEO record WHERE ...

That's all! No any loading, manipulations, manual handling - an implementation is hidden in Spring - very simple and reliable.