1.实现分页
方法一：使用Pageable
使用Pageable作为入参传入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; /** * 查询用户列表 */ @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 { /** * 查询用户列表 */ Page<User> queryAll(Pageable pageable); } |
Controller
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/** * 查询用户列表 */ @GetMapping("/userList") public Page<User> queryAll(){ //注意，前端页面的页面是从1开始，而JPA是从0开始 Pageable pageable = PageRequest.of(0,5); //查询用户列表 return userService.queryAll(pageable); } |
方法二：以元模型概念为基础的Criteria 查询方法
UserRepository额外继承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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/** * 查询用户列表 */ @Override public Page<User> queryAll(String name,String age,Pageable pageable) { Specification<User> specification = (Specification<User>)(root, query, criteriaBuilder) ->{ List<Predicate> list = new ArrayList<>(); // 第一个name为User实体对象中的字段，第二个name为参数 Predicate p1 = criteriaBuilder.equal(root.get("name"),name); list.add(p1); // if (!age.equals(null)) { // // 此处为查询serverName中含有age的数据 // Predicate p2 = criteriaBuilder.like(root.get("age"),"%"+age+"%" ); // list.add(p2); // } return criteriaBuilder.and(list.toArray(new Predicate[0])); }; return userRepository.findAll(specification,pageable); } |
其它代码如方法一，不用动。
**方法一：实体类加@Enumerated注解
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package com.kinglead.demo.enums;import com.fasterxml.jackson.annotation.JsonValue;public interface BaseEnum<K> { /** * 真正与数据库进行映射的值 * * @return */ K getCode(); /** * 显示的信息 * * @return */ @JsonValue //jackson返回报文response的设置 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 //无参构造函数 @AllArgsConstructor //所以参数构造函数 @Entity //声明为JPA实体 @Table(name = "t_user") //该标注与@Entity标注并列使用，用于指明数据库的表名 public class User implements Serializable { private static final long serialVersionUID = -21070736985722463L; @Id //指明主键 @GeneratedValue(strategy= GenerationType.AUTO) private Long id; @Column(name = "name", columnDefinition = "姓名") //指明字段 private String name; @Column(name = "age", columnDefinition = "年龄") //指明字段 private Long age; @Column(name = "email", columnDefinition = "邮箱") //指明字段 private String email; @Column(name = "gender", columnDefinition = "性别") //指明字段 @Enumerated(EnumType.STRING) private GenderEnum gender; } |
方法二：使用jpa2.1规范里面的属性转换器
将方法一中实体对象User的gender成员变量上的注解@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); } } |
上面的转换器只是针对某一种枚举进行转换，如果写成通用的转换器呢，后续研究
源码地址：https://github.com/kinglead2012/myblog
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：https://www.cnblogs.com/kinglead/p/13748214.html
