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
UserRepository
package com.kinglead.demo.dao; ​ import com.kinglead.demo.entity.User; import org.springframework.data.jpa.repository.JpaRepository; ​ public interface UserRepository extends JpaRepository{ }
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; ​ /** * 查询用户列表 */ @Override public PagequeryAll(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 { /** * 查询用户列表 */ PagequeryAll(Pageable pageable); }
Controller
/** * 查询用户列表 */ @GetMapping("/userList") public PagequeryAll(){ //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<>
package com.kinglead.demo.dao; &#8203; import com.kinglead.demo.entity.User; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.JpaSpecificationExecutor; &#8203; public interface UserRepository extends JpaRepository, JpaSpecificationExecutor { }
UserServiceImpl
/** * 查询用户列表 */ @Override public PagequeryAll(String name,String age,Pageable pageable) { Specification specification = (Specification )(root, query, criteriaBuilder) ->{ List 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。
2.枚举转换
**方法一:实体类加@Enumerated注解
package com.kinglead.demo.enums; import com.fasterxml.jackson.annotation.JsonValue; public interface BaseEnum{ /** * 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(); }
package com.kinglead.demo.enums; &#8203; public enum GenderEnum implements BaseEnum{ &#8203; MALE("MALE","男"), FEMALE("FEMALE","女"); &#8203; &#8203; private final String code; private final String displayName; &#8203; GenderEnum(String code, String displayName) { this.code = code; this.displayName = displayName; } &#8203; @Override public String getCode() { return code; } &#8203; @Override public String getDisplayName() { return displayName; }}
package com.kinglead.demo.entity; &#8203; import com.kinglead.demo.enums.GenderEnum; import lombok.AllArgsConstructor; import lombok.Data; import lombok.NoArgsConstructor; &#8203; import javax.persistence.*; import java.io.Serializable; &#8203; @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; &#8203; @Id //指明主键 @GeneratedValue(strategy= GenerationType.AUTO) private Long id; &#8203; @Column(name = "name", columnDefinition = "姓名") //指明字段 private String name; &#8203; @Column(name = "age", columnDefinition = "年龄") //指明字段 private Long age; &#8203; @Column(name = "email", columnDefinition = "邮箱") //指明字段 private String email; &#8203; @Column(name = "gender", columnDefinition = "性别") //指明字段 @Enumerated(EnumType.STRING) private GenderEnum gender; &#8203; }
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
package com.kinglead.demo.config; &#8203; import com.kinglead.demo.enums.GenderEnum; &#8203; import javax.persistence.AttributeConverter; import javax.persistence.Converter; &#8203; @Converter(autoApply = true) public class ColorConverter implements AttributeConverter{ &#8203; @Override public String convertToDatabaseColumn(GenderEnum attribute) { return attribute.getCode(); } &#8203; @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。