Spring boot JPA實現(xiàn)分頁和枚舉轉(zhuǎn)換代碼示例
1.實現(xiàn)分頁
方法一:使用Pageable
使用Pageable作為入?yún)魅隦epository,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; /** * 查詢用戶列表 */ @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 { /** * 查詢用戶列表 */ Page<User> queryAll(Pageable pageable); }
Controller
/** * 查詢用戶列表 */ @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); //查詢用戶列表 return userService.queryAll(pageable); }
方法二:以元模型概念為基礎(chǔ)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
/** * 查詢用戶列表 */ @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實體對象中的字段,第二個name為參數(shù) 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的數(shù)據(jù) // Predicate p2 = criteriaBuilder.like(root.get("age"),"%"+age+"%" ); // list.add(p2); // } return criteriaBuilder.and(list.toArray(new Predicate[0])); }; return userRepository.findAll(specification,pageable); }
其它代碼如方法一,不用動。
2.枚舉轉(zhuǎn)換
**方法一:實體類加@Enumerated注解
package com.kinglead.demo.enums; import com.fasterxml.jackson.annotation.JsonValue; public interface BaseEnum<K> { /** * 真正與數(shù)據(jù)庫進行映射的值 * * @return */ K getCode(); /** * 顯示的信息 * * @return */ @JsonValue //jackson返回報文response的設(shè)置 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 //添加getter、setter方法 @NoArgsConstructor //無參構(gòu)造函數(shù) @AllArgsConstructor //所以參數(shù)構(gòu)造函數(shù) @Entity //聲明為JPA實體 @Table(name = "t_user") //該標注與@Entity標注并列使用,用于指明數(shù)據(jù)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") //指明字段 private String name; @Column(name = "age", columnDefinition = "年齡") //指明字段 private Long age; @Column(name = "email", columnDefinition = "郵箱") //指明字段 private String email; @Column(name = "gender", columnDefinition = "性別") //指明字段 @Enumerated(EnumType.STRING) private GenderEnum gender; }
方法二:使用jpa2.1規(guī)范里面的屬性轉(zhuǎn)換器
將方法一中實體對象User的gender成員變量上的注解@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(zhuǎn)換器只是針對某一種枚舉進行轉(zhuǎn)換,如果寫成通用的轉(zhuǎn)換器呢,后續(xù)研究
源碼地址:https://github.com/kinglead2012/myblog
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