Spring boot JPA实现分页和枚举转换代码示例

Spring boot JPA实现分页和枚举转换代码示例

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接收

UserRepository

package com.kinglead.demo.dao;

​

import com.kinglead.demo.entity.User;

import org.springframework.data.jpa.repositorySYpzp.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 Page 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 {

/**

* 查询用户列表

*/

Page queryAll(Pageable pageable);

}

Controller

/**

* 查询用户列表

*/

@GetMapping("/userList")

public Page 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<>

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, JpaSpecificationExecutor {

}

UserServiceImpl

/**

* 查询用户列表

*/

@Override

public Page queryAll(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;

​

public enum GenderEnum implements BaseEnum {

​

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 //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

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 {

​

@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

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