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
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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
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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
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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
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/** * 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的Criteria 查詢方法
UserRepository額外繼承JpaSpecificationExecutor<>
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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
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/** * 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 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的數據 // 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。
**方法一：實體類加@Enumerated注解
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package com.kinglead.demo.enums;import com.fasterxml.jackson.annotation.JsonValue;public interface BaseEnum<K> { /** * 真正與數據庫進行映射的值 * * @return */ K getCode(); /** * 顯示的信息 * * @return */ @JsonValue //jackson返回報文response的設置 String getDisplayName();} |
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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; }} |
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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 //無參構造函數 @AllArgsConstructor //所以參數構造函數 @Entity //聲明為JPA實體 @Table(name = "t_user") //該標注與@Entity標注并列使用，用于指明數據庫的表名 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規范里面的屬性轉換器
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
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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枚舉進行轉換，如果寫成通用的轉換器呢，后續研究
源碼地址：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，也希望大家多多支持服務器之家。
原文鏈接：https://www.cnblogs.com/kinglead/p/13748214.html
