Spring boot JPA實現分頁和列舉轉換程式碼示例
阿新 • • 發佈:2020-10-02
1.實現分頁
方法一:使用Pageable
使用Pageable作為入參傳入Repository,返回值用Page<T>接收
UserRepository
package com.kinglead.demo.dao; import com.kinglead.demo.entity.User; import org.springframework.data.jpa.repository.JpaRepository; public interface UserRepository extends JpaRepository<User,Long> { }
UserServiceImpl
package com.kinglead.demo.service.impl; import com.kinglead.demo.dao.UserRepository; import com.kinglead.demo.entity.User; import com.kinglead.demo.service.UserService; import org.springframework.data.domain.Page; import org.springframework.data.domain.Pageable; import org.springframework.stereotype.Service; import javax.annotation.Resource; @Service public class UserServiceImpl implements UserService { @Resource private UserRepository userRepository; /** * 查詢使用者列表 */ @Override public Page<User> queryAll(Pageable pageable) { return userRepository.findAll(pageable); } }
UserService
package com.kinglead.demo.service; import com.kinglead.demo.entity.User; import org.springframework.data.domain.Page; import org.springframework.data.domain.Pageable; import java.util.List; import java.util.Map; public interface UserService { /** * 查詢使用者列表 */ Page<User> queryAll(Pageable pageable); }
Controller
/** * 查詢使用者列表 */ @GetMapping("/userList") public Page<User> queryAll(){ //注意,前端頁面的頁面是從1開始,而JPA是從0開始 Pageable pageable = PageRequest.of(0,5); //查詢使用者列表 return userService.queryAll(pageable); }
方法二:以元模型概念為基礎的Criteria 查詢方法
UserRepository額外繼承JpaSpecificationExecutor<>
package com.kinglead.demo.dao; import com.kinglead.demo.entity.User; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.JpaSpecificationExecutor; public interface UserRepository extends JpaRepository<User,Long>,JpaSpecificationExecutor<User> { }
UserServiceImpl
/** * 查詢使用者列表 */ @Override public Page<User> queryAll(String name,String age,Pageable pageable) { Specification<User> specification = (Specification<User>)(root,query,criteriaBuilder) ->{ List<Predicate> list = new ArrayList<>(); // 第一個name為User實體物件中的欄位,第二個name為引數 Predicate p1 = criteriaBuilder.equal(root.get("name"),name); list.add(p1); // if (!age.equals(null)) { // // 此處為查詢serverName中含有age的資料 // Predicate p2 = criteriaBuilder.like(root.get("age"),"%"+age+"%" ); // list.add(p2); // } return criteriaBuilder.and(list.toArray(new Predicate[0])); }; return userRepository.findAll(specification,pageable); }
其它程式碼如方法一,不用動。
2.列舉轉換
**方法一:實體類加@Enumerated註解
package com.kinglead.demo.enums; import com.fasterxml.jackson.annotation.JsonValue; public interface BaseEnum<K> { /** * 真正與資料庫進行對映的值 * * @return */ K getCode(); /** * 顯示的資訊 * * @return */ @JsonValue //jackson返回報文response的設定 String getDisplayName(); }
package com.kinglead.demo.enums; public enum GenderEnum implements BaseEnum<String> { MALE("MALE","男"),FEMALE("FEMALE","女"); private final String code; private final String displayName; GenderEnum(String code,String displayName) { this.code = code; this.displayName = displayName; } @Override public String getCode() { return code; } @Override public String getDisplayName() { return displayName; }}
package com.kinglead.demo.entity; import com.kinglead.demo.enums.GenderEnum; import lombok.AllArgsConstructor; import lombok.Data; import lombok.NoArgsConstructor; import javax.persistence.*; import java.io.Serializable; @Data //新增getter、setter方法 @NoArgsConstructor //無參建構函式 @AllArgsConstructor //所以引數建構函式 @Entity //宣告為JPA實體 @Table(name = "t_user") //該標註與@Entity標註並列使用,用於指明資料庫的表名 public class User implements Serializable { private static final long serialVersionUID = -21070736985722463L; @Id //指明主鍵 @GeneratedValue(strategy= GenerationType.AUTO) private Long id; @Column(name = "name",columnDefinition = "姓名") //指明欄位 private String name; @Column(name = "age",columnDefinition = "年齡") //指明欄位 private Long age; @Column(name = "email",columnDefinition = "郵箱") //指明欄位 private String email; @Column(name = "gender",columnDefinition = "性別") //指明欄位 @Enumerated(EnumType.STRING) private GenderEnum gender; }
方法二:使用jpa2.1規範裡面的屬性轉換器
將方法一中實體物件User的gender成員變數上的註解@Enumerated(EnumType.STRING)去掉
package com.kinglead.demo.config; import com.kinglead.demo.enums.GenderEnum; import javax.persistence.AttributeConverter; import javax.persistence.Converter; @Converter(autoApply = true) public class ColorConverter implements AttributeConverter<GenderEnum,String> { @Override public String convertToDatabaseColumn(GenderEnum attribute) { return attribute.getCode(); } @Override public GenderEnum convertToEntityAttribute(String dbData) { return GenderEnum.valueOf(dbData); } }
上面的轉換器只是針對某一種列舉進行轉換,如果寫成通用的轉換器呢,後續研究
原始碼地址:https://github.com/kinglead2012/myblog
以上就是本文的全部內容,希望對大家的學習有所幫助,也希望大家多多支援我們。