JPA框架下使用纯粹的原生SQL

　　最近遇到一个需求，查询数据库中对应表的字段是动态的，项目使用的框架使用JPA+Spring Boot，JPA自带原生SQL支持的传入参数是强类型的，无法用于查询语句的字段更改，因为插入字符串的话带有单引号，需要另外定义原生SQL

因此我们创建一个查询类

import com.weiqitonggame.trade.model.WebInfo;
import org.springframework.stereotype.Component;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Component  //标记为组件，spring启动时会将该类扫描进容器
public class InformationDaoEM {
    
    @PersistenceContext //注入的是实体管理器,执行持久化操作
    EntityManager entityManager;

    public String getInfoWebWaring(String column){
        String SQL = "SELECT "+column+" FROM config LIMIT 1";
        Object obj = entityManager.createNativeQuery(SQL).getSingleResult();

        return String.valueOf(obj);
    }
    
    public WebInfo getWebInfo(String [] args){

        String SQL = "SELECT id, "+
                args[0]+" log_url, "+
                args[1]+" title, "+
                args[2]+" key_word, "+
                args[3]+" description, "+
                args[4]+" address, "+
                args[5]+" contact "+
                "FROM config LIMIT 1";

        WebInfo webInfo = (WebInfo) entityManager.createNativeQuery(SQL,WebInfo.class).getSingleResult();

        return webInfo;
    }

}

其中
EntityManager.createNativeQuery(SQL)返回的是Object对象
entityManager.createNativeQuery(SQL,WebInfo.class)返回的是映射后的实例对象
实体类WebInfo需要进行以下处理，确保被扫描进spring容器

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.experimental.Accessors;

import javax.persistence.*;

@Data //生成读写方法
@AllArgsConstructor //生成全参构造方法
@NoArgsConstructor //生成无参构造方法
@Accessors(chain = true) 
@Entity(name = "tableName") //标记为entity
public class WebInfo {
    @Id
    @GeneratedValue(strategy= GenerationType.AUTO)
    @Column(name = "id") //查询结果对应字段
    private Integer id;
    @Column(name = "log_url")
    private String logUrl;
    @Column(name = "title")
    private String title;
    @Column(name = "key_word")
    private String keyWord;
    @Column(name = "description")
    private String description;
    @Column(name = "address")
    private String address;
    @Column(name = "contact")
    private String contact;

}

Query.getSingleResult() 执行SQL语句，返回一个查询结果，常用的还有以下方法
Query.getResultList() () 执行SQL语句，返回一个List集合
Query.getFirstResult() () 执行SQL语句，返回一个系列结果集合的第一个

调用方式如下:

import org.springframework.stereotype.Service;
import com.weiqitonggame.trade.service.InformationService;
import org.springframework.beans.factory.annotation.Autowired;
import com.weiqitonggame.trade.dao.InformationDaoEM;
import com.weiqitonggame.trade.model.WebInfo;

@Service  //标记为service
public class InformationServiceImpl implements InformationService {
    
    @Autowired  //注入informationDaoEM
    private InformationDaoEM informationDaoEM;

    @Override
    public String getWebWaring(String column) {

        return informationDaoEM.getInfoWebWaring(column);
    }

    @Override
    public WebInfo getWebInfo(String[] args) {

        return informationDaoEM.getWebInfo(args);
    }

    


}

因此我们创建一个查询类

import com.weiqitonggame.trade.model.WebInfo;
import org.springframework.stereotype.Component;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Component  //标记为组件，spring启动时会将该类扫描进容器
public class InformationDaoEM {
    
    @PersistenceContext //注入的是实体管理器,执行持久化操作
    EntityManager entityManager;

    public String getInfoWebWaring(String column){
        String SQL = "SELECT "+column+" FROM config LIMIT 1";
        Object obj = entityManager.createNativeQuery(SQL).getSingleResult();

        return String.valueOf(obj);
    }
    
    public WebInfo getWebInfo(String [] args){

        String SQL = "SELECT id, "+
                args[0]+" log_url, "+
                args[1]+" title, "+
                args[2]+" key_word, "+
                args[3]+" description, "+
                args[4]+" address, "+
                args[5]+" contact "+
                "FROM config LIMIT 1";

        WebInfo webInfo = (WebInfo) entityManager.createNativeQuery(SQL,WebInfo.class).getSingleResult();

        return webInfo;
    }

}

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.experimental.Accessors;

import javax.persistence.*;

@Data //生成读写方法
@AllArgsConstructor //生成全参构造方法
@NoArgsConstructor //生成无参构造方法
@Accessors(chain = true) 
@Entity(name = "tableName") //标记为entity
public class WebInfo {
    @Id
    @GeneratedValue(strategy= GenerationType.AUTO)
    @Column(name = "id") //查询结果对应字段
    private Integer id;
    @Column(name = "log_url")
    private String logUrl;
    @Column(name = "title")
    private String title;
    @Column(name = "key_word")
    private String keyWord;
    @Column(name = "description")
    private String description;
    @Column(name = "address")
    private String address;
    @Column(name = "contact")
    private String contact;

}

调用方式如下:

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import org.springframework.stereotype.Service;
import com.weiqitonggame.trade.service.InformationService;
import org.springframework.beans.factory.annotation.Autowired;
import com.weiqitonggame.trade.dao.InformationDaoEM;
import com.weiqitonggame.trade.model.WebInfo;

@Service  //标记为service
public class InformationServiceImpl implements InformationService {
    
    @Autowired  //注入informationDaoEM
    private InformationDaoEM informationDaoEM;

    @Override
    public String getWebWaring(String column) {

        return informationDaoEM.getInfoWebWaring(column);
    }

    @Override
    public WebInfo getWebInfo(String[] args) {

        return informationDaoEM.getWebInfo(args);
    }

    


}

JPA框架下使用纯粹的原生SQL

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