如何在Spring Boot应用程序中手动注册非标准的SQL函数? [英] How to register non-standarized SQL functions manually in Spring Boot application?

问题描述

我在当前的spring-boot项目中使用JPA查询.如何添加非标准化的SQL函数，如 GROUP_CONCAT ?

I'm using JPA query in my current spring-boot project. How can I add non-standardized SQL functions like GROUP_CONCAT?

在我之前的问题之前: 如何在JPA查询中的单行逗号分隔列表中显示列结果

Prior, to my previous problem : How to show a column result in a one line comma separated list in JPA query

我发现GROUP_CONCAT不是JPA查询中的注册函数，但是可以通过手动注册来访问它.我已经尝试了以下链接，但对我不起作用:

I found that GROUP_CONCAT is not a registered function in JPA query but could be accessed by registering it manually. I already tried following links but didn't work for me :

如何添加非标准化sql Spring Boot应用程序中有什么功能?

使用JPA和Hibernate注册SQL函数

https://thoughts-on-java.org/database-functions/

https://vladmihalcea.com/hibernate-sql- function-jpql-criteria-api-query/

1.

public class SqlFunctionsMetadataBuilderContributor
        implements MetadataBuilderContributor {

    @Override
    public void contribute(MetadataBuilder metadataBuilder) {
        metadataBuilder.applySqlFunction(
                "group_concat",
                new StandardSQLFunction(
                        "group_concat",
                        StandardBasicTypes.STRING
                )
        );
    }
}

2.

 public String render(Type firstArgumentType, List arguments, SessionFactoryImplementor factory)
            throws QueryException {
        if (arguments.size() < 1) {
            throw new QueryException(new IllegalArgumentException("group_concat should have at least one arg"));
        }

        StringBuilder builder = new StringBuilder();
        if (arguments.size() > 1 && arguments.get(0).equals("'distinct'")) {
            builder.append("distinct ");
            builder.append(arguments.get(1));
        } else {
            builder.append(arguments.get(0));
        }

        return "group_concat(" + builder.toString() + ")";
    }

3.

@Configuration
public class DataSource {
    @Bean
    public JpaVendorAdapter jpaVendorAdapter() {
        AbstractJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
        adapter.setShowSql(true);
        adapter.setDatabase(Database.MYSQL);
        // package to CustomMysqlDialect
        adapter.setDatabasePlatform("com.myprojet.admin.configuration.RegisterSqlFunction");
        adapter.setGenerateDdl(false);
        return adapter;
    }
}

    public RegisterSqlFunction() {
        super();

         registerFunction("group_concat, new StandardSQLFunction("group_concat", 
       StandardBasicTypes.STRING));
    }

除了在JPA查询中使用group_concat之外，我都是这样.

I except using group_concat with JPA query.

推荐答案

您可以在我的高性能Java持久性GitHub存储库.

根据您的情况，您无需自定义JpaPlatform.应该将其设置为HibernateJpaPlatform.

In your case, you don't need to customize the JpaPlatform. That should be set to the HibernateJpaPlatform.

您可以按照本文或通过application.properties配置文件:

You can register the MetadataBuilderContributer either programaticallly as explained in this article or via the application.properties configuration file:

hibernate.metadata_builder_contributor=com.vladmihalcea.book.hpjp.SqlFunctionsMetadataBuilderContributor

这篇关于如何在Spring Boot应用程序中手动注册非标准的SQL函数?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！