SpringBoot中JPA使⽤动态SQL查询
可以重点关注⽅法⼆，把原⽣sql传⼊数据库去查询
好处是：更加灵活坏处是：拼接sql⽐较痛苦，也容易出问题，⽐如拼接的sql某些字段不存在或者拼接后语法不符合sql语句package com.aircas.satellitemanagement.jpa;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import javax.persistence.EntityManager;
import javax.persistence.Query;
import java.util.List;
@RestController
@RequestMapping(value = "/user")
public class UserController {
@Autowired
LocalContainerEntityManagerFactoryBean entityManagerFactory;
@GetMapping(value = "/all/4")
public List<User> exec() {
EntityManager em = NativeEntityManagerFactory().createEntityManager();
StringBuilder sqljoint = new StringBuilder(300);
sqljoint.append("SELECT * FROM user");
String sql = String();
// User是我⾃⼰定义的entity bean
Query query = em.createNativeQuery(sql, User.class);
List<User> obj = ResultList();
return obj;
}
}
package com.aircas.satellitemanagement.jpa;
import lombok.Data;
import lombok.ToString;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name = "user")
@Data
@ToString
public class User {
@Id
private String id;
private String name;
private String startTime;
springboot是啥
}
数据库表结构
查询结果，是get接⼝，我就直接⽤浏览器访问了
注意：实际应⽤中，会⽐较复杂，⼀般来说前台会给后台传⼀些参数⽐如name=xxx，后台需要去拼接sql语句
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在后续的使⽤中发现 LocalContainerEntityManagerFactoryBean 会有并发问题，然后尝试了直接使⽤ EntityManager，发现可以⽤，⽬前没啥问题，修改后的如下package com.aircas.satellitemanagement.jpa;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.persistence.EntityManager;
import javax.persistence.Query;
import java.util.List;
@RestController
@RequestMapping(value = "/user")
public class UserController {
@Autowired
EntityManager entityManager;
@GetMapping(value = "/all/4")
public List<User> exec() {
StringBuilder sqljoint = new StringBuilder(300);
sqljoint.append("SELECT * FROM user");
String sql = String();
// User是我⾃⼰定义的entity bean
Query query = ateNativeQuery(sql, User.class);
List<User> obj = ResultList();
return obj;
}
}

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