閱讀全文，約 23?分鐘

這是江帥帥的第009篇原創(chuàng)

Spring Boot 整合持久層開發(fā)

1、ORM

ORM（Object/Relation Mapping，對象/關(guān)系型數(shù)據(jù)庫映射）是一種規(guī)范，用于描述面向?qū)ο笳Z言到關(guān)系型數(shù)據(jù)庫的映射。

我們主要實現(xiàn)持久化類和數(shù)據(jù)表之間的映射，達到通過持久化類實現(xiàn)對數(shù)據(jù)表的操作。

ORM 有如下幾個基本的映射關(guān)系

數(shù)據(jù)表映射類
數(shù)據(jù)表的行映射對象（實例）
數(shù)據(jù)表的列（字段）映射對象的屬性

常見的 ORM 框架

Hibernate 是一個開源的框架
JPA（Java Persistence API，Java 持久化規(guī)范）

2、Spring Data JPA

亮點：極大地簡化了 JPA 的使用，在幾乎不用寫接口實現(xiàn)的情況下，就能完成對數(shù)據(jù)的訪問和操作。

Spring Data JPA 是 Spring Data 下的一個小模塊，Spring Data 提供了訪問操作數(shù)據(jù)的統(tǒng)一規(guī)范。

Spring Data 通過提供 Respository 接口來約定數(shù)據(jù)訪問的統(tǒng)一標準。

Respository 接口中常用的幾個子接口：

CrudRepository
PagingAndSortingRepository
JpaRepository

我們只需要定義數(shù)據(jù)訪問接口，然后實現(xiàn) Spring Data 提供的這些接口，然后就能實現(xiàn)對數(shù)據(jù)的操作了。

2.1 CrudRepository

使用 CrudRepository 接口訪問數(shù)據(jù)。

1）編輯 pom.xml 文件

添加 mysql-connector-java 和 spring-boot-starter-data-jpa 依賴模塊，具體如下：


<project?xmlns="http://maven.apache.org/POM/4.0.0"
?????????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
?????????xsi:schemaLocation="http://maven.apache.org/POM/4.0.0?http://maven.apache.org/xsd/maven-4.0.0.xsd">
????<modelVersion>4.0.0modelVersion>

????<groupId>com.nxgroupId>
????<artifactId>springbootdataartifactId>
????<version>1.0-SNAPSHOTversion>
????<parent>
????????<groupId>org.springframework.bootgroupId>
????????<artifactId>spring-boot-starter-parentartifactId>
????????<version>2.2.6.RELEASEversion>
????????<relativePath/>
????parent>
????<properties>
????????<project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
????????<project.reporting.outputEncoding>UTF-8project.reporting.outputEncoding>
????????<java.version>1.8java.version>
????properties>

????<dependencies>
????????
????????<dependency>
????????????<groupId>org.springframework.bootgroupId>
????????????<artifactId>spring-boot-starter-webartifactId>
????????dependency>

????????
????????<dependency>
????????????<groupId>mysqlgroupId>
????????????<artifactId>mysql-connector-javaartifactId>
????????dependency>

????????
????????<dependency>
????????????<groupId>org.springframework.bootgroupId>
????????????<artifactId>spring-boot-starter-thymeleafartifactId>
????????dependency>

????????
????????<dependency>
????????????<groupId>org.springframework.bootgroupId>
????????????<artifactId>spring-boot-starter-data-jpaartifactId>
????????dependency>

????????<dependency>
????????????<groupId>junitgroupId>
????????????<artifactId>junitartifactId>
????????????<scope>testscope>
????????dependency>
????dependencies>

project>

2）編輯 application.properties 文件

添加數(shù)據(jù)源與 JPA 等基本配置信息。

####################
###?數(shù)據(jù)源信息配置?###
####################
#?數(shù)據(jù)庫地址
spring.datasource.url=jdbc:mysql://localhost:3306/springbootdata?characterEncoding=utf8&useSSL=false&serverTimezone=UTC&rewriteBatchedStatements=true
#?用戶名
spring.datasource.username=root
#?密碼
spring.datasource.password=1234
#?數(shù)據(jù)庫驅(qū)動
spring.datasource.driverClassName=com.mysql.cj.jdbc.Driver
#?指定連接池中最大的活躍連接數(shù).
spring.datasource.max-active=20
#?指定連接池最大的空閑連接數(shù)量.
spring.datasource.max-idle=8
#?指定必須保持連接的最小值
spring.datasource.min-idle=8
#?指定啟動連接池時，初始建立的連接數(shù)量
spring.datasource.initial-size=10

####################
###?JPA持久化配置?###
####################
#?指定數(shù)據(jù)庫的類型
spring.jpa.database=MySQL
#?指定是否需要在日志中顯示sql語句
spring.jpa.show-sql=true
#?指定自動創(chuàng)建|更新|驗證數(shù)據(jù)庫表結(jié)構(gòu)等配置，配置成update
#?表示如果數(shù)據(jù)庫中存在持久化類對應的表就不創(chuàng)建，不存在就創(chuàng)建對應的表
spring.jpa.hibernate.ddl-auto=update
#?Naming?strategy
#?指定命名策略
spring.jpa.hibernate.naming-strategy=org.hibernate.cfg.ImprovedNamingStrategy
#?指定數(shù)據(jù)庫方言
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect

3）創(chuàng)建 User 持久化類

package?nx.bean;

import?java.io.Serializable;

import?javax.persistence.Entity;
import?javax.persistence.GeneratedValue;
import?javax.persistence.GenerationType;
import?javax.persistence.Id;
import?javax.persistence.Table;

@Entity
//?此注解，會在?Spring?Boot?項目加載后會自動根據(jù)持久化類創(chuàng)建數(shù)據(jù)表
@Table(name="tb_user")?
public?class?User?implements?Serializable{

????private?static?final?long?serialVersionUID?=?1L;

????/**
?????*?使用@Id指定主鍵。使用代碼@GeneratedValue(strategy=GenerationType.AUTO)
?????*?指定主鍵的生成策略，mysql默認的是自增長。
?????*/
????@Id
????@GeneratedValue(strategy?=?GenerationType.IDENTITY)
????private?int?id;
????private?String?username;
????private?String?loginName;
????private?char?sex;
????private?int?age;

????//?getXxx?&?setXxx?方法
}

4）創(chuàng)建 UserRepository 數(shù)據(jù)訪問接口

在這里，我們不需要提供實現(xiàn)，只要直接繼承數(shù)據(jù)訪問接口就好。

package?nx.repository;

import?nx.bean.User;
import?org.springframework.data.repository.CrudRepository;

public?interface?UserRepository?extends?CrudRepository<User,?Integer>{
}

5）創(chuàng)建 UserService 業(yè)務層類

package?nx.service;

import?java.util.Optional;

import?javax.annotation.Resource;
import?javax.transaction.Transactional;

import?nx.bean.User;
import?nx.repository.UserRepository;
import?org.springframework.stereotype.Service;

@Service
public?class?UserService?{

????//?注入UserRepository
????@Resource
????private?UserRepository?userRepository;

????/**
?????*?save\update\delete?
?????*?方法需要綁定事務，使用@Transactional進行事務的綁定
?????*?
?????*?保存對象
?????*?@param?User
?????*?@return?包含自動生成的?id?的?User????????
?????*/
????@Transactional
????public?User?save(User?User)?{
????????return?userRepository.save(User);
????}

????/**
?????*?根據(jù)id刪除對象
?????*/
????@Transactional
????public?void?delete(int?id)?{
????????userRepository.deleteById(id);

????}

????/**
?????*?查詢所有數(shù)據(jù)
?????*/
????public?Iterable?getAll()?{
????????return?userRepository.findAll();
????}

????/**
?????*?根據(jù)id查詢數(shù)據(jù)
?????*/
????public?User?getById(Integer?id)?{
????????//?根據(jù)id查詢出對應的持久化對象
????????Optional?op?=?userRepository.findById(id);
????????return?op.get();
????}

????/**
?????*?修改用戶對象數(shù)據(jù)，持久化對象修改會自動更新到數(shù)據(jù)庫
?????*/
????@Transactional
????public?void?update(User?user)?{
????????//?直接調(diào)用持久化對象的set方法修改對象的數(shù)據(jù)
????????user.setUsername("帥帥");
????????user.setLoginName("shuaishuai");
????}
}

6）創(chuàng)建控制器類

package?nx.controller;

import?javax.annotation.Resource;

import?nx.bean.User;
import?nx.service.UserService;
import?org.springframework.web.bind.annotation.RequestMapping;
import?org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/user")
public?class?UserController?{

????//?注入UserService
????@Resource
????private?UserService?userService;

????@RequestMapping("/save")
????public?String?save()?{
????????User?user?=?new?User();
????????user.setLoginName("mason");
????????user.setUsername("帥帥");
????????user.setSex('男');
????????user.setAge(18);
????????user?=?userService.save(user);
????????return?"保存數(shù)據(jù)成功！";
????}

????@RequestMapping("/update")
????public?String?update()?{
????????//?修改的對象必須是持久化對象，所以先從數(shù)據(jù)庫查詢出id為1的對象進行修改
????????User?user?=?userService.getById(1);
????????userService.update(user);
????????return?"修改數(shù)據(jù)成功!";
????}

????@RequestMapping("/delete")
????public?String?delete()?{
????????userService.delete(1);
????????return?"刪除數(shù)據(jù)成功！";
????}

????@RequestMapping("/getAll")
????public?Iterable?getAll()?{
????????return?userService.getAll();
????}
}

7）創(chuàng)建數(shù)據(jù)庫

CREATE?DATABASE?springbootdata;

8）訪問測試

瀏覽器，輸入 http://localhost:8080/user/getAll

2.2 PagingAndSortingRepository

PagingAndSortingRepository 繼承了 CrudRepository 接口，它還能實現(xiàn)分頁和排序的功能。

1）編輯 pom.xml 文件

與 CrudRepository 接口案例一樣

2）編輯 application.properties 文件

與 CrudRepository 接口案例一樣

3）創(chuàng)建 Article 持久化類

package?nx.bean;

import?java.io.Serializable;
import?java.util.Date;

import?javax.persistence.Entity;
import?javax.persistence.GeneratedValue;
import?javax.persistence.GenerationType;
import?javax.persistence.Id;
import?javax.persistence.Table;

/**
?*??商品對象
?*/
@Entity
@Table(name="tb_article")
public?class?Article?implements?Serializable{

????private?static?final?long?serialVersionUID?=?1L;

????@Id
????@GeneratedValue(strategy?=?GenerationType.IDENTITY)
????private?int?id;
????private?String?title;
????private?String?supplier;
????private?Double?price;
????private?String?locality;
????private?Date?putawayDate;
????private?int?storage;
????private?String?image;
????private?String?description;
????private?Date?createDate;

????//?getXxx?&?setXxx?方法
}

4）定義 ArticleRepository 數(shù)據(jù)訪問接口

package?nx.repository;

import?nx.bean.Article;
import?org.springframework.data.repository.PagingAndSortingRepository;

public?interface?ArticleRepository?extends?PagingAndSortingRepository<Article,?Integer>?{
}

5）定義 ArticleService 業(yè)務層類

package?nx.service;

import?javax.annotation.Resource;

import?nx.bean.Article;
import?nx.repository.ArticleRepository;
import?org.springframework.data.domain.Page;
import?org.springframework.data.domain.Pageable;
import?org.springframework.data.domain.Sort;
import?org.springframework.stereotype.Service;

@Service
public?class?ArticleService?{

????//?注入數(shù)據(jù)訪問層接口對象?
????@Resource
????private?ArticleRepository?articleRepository;

????public?Iterable?findAllSort(Sort?sort)?{
????????return?articleRepository.findAll(sort);
????}

????public?Page?findAll(Pageable?page)?{
????????return?articleRepository.findAll(page);
????}
}

6）定義 ArticleController 控制器類

package?nx.controller;

import?java.util.List;
import?javax.annotation.Resource;
import?nx.bean.Article;
import?nx.service.ArticleService;
import?org.springframework.data.domain.Page;
import?org.springframework.data.domain.PageRequest;
import?org.springframework.data.domain.Pageable;
import?org.springframework.data.domain.Sort;
import?org.springframework.web.bind.annotation.RequestMapping;
import?org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/article")
public?class?ArticleController?{

????//?注入ArticleService
????@Resource
????private?ArticleService?articleService;

????@RequestMapping("/sort")
????public?Iterable?sortArticle()?{
????????//?指定排序參數(shù)對象：根據(jù)id，進行降序查詢
????????Sort.Order?sort?=?new?Sort.Order(Sort.Direction.DESC,?"id");
????????Iterable?articleDatas?=?articleService.findAllSort(sort.withProperties("id"));
????????return?articleDatas;
????}

????@RequestMapping("/pager")
????public?List?sortPagerArticle(int?pageIndex)?{
????????//?指定排序參數(shù)對象：根據(jù)id，進行降序查詢

????????Sort.Order?sort?=?new?Sort.Order(Sort.Direction.DESC,?"id");
????????Pageable?page?=?PageRequest.of(pageIndex?-?1,?2,?Sort.by(sort));
????????Page?articleDatas?=?articleService.findAll(page);
????????System.out.println("查詢總頁數(shù):"?+?articleDatas.getTotalPages());
????????System.out.println("查詢總記錄數(shù):"?+?articleDatas.getTotalElements());
????????System.out.println("查詢當前第幾頁:"?+?articleDatas.getNumber()?+?1);
????????System.out.println("查詢當前頁面的記錄數(shù):"?+?articleDatas.getNumberOfElements());
????????//?查詢出的結(jié)果數(shù)據(jù)集合
????????List?articles?=?articleDatas.getContent();
????????System.out.println("查詢當前頁面的集合:"?+?articles);
????????return?articles;
????}
}

7）訪問測試

往數(shù)據(jù)表中添加一些數(shù)據(jù)，然后就可以看到具體效果了。（此處略）

來源公眾號：江帥帥（ID：NXJSS666）

更多精彩?

在公眾號【程序員編程】對話框輸入以下關(guān)鍵詞

查看更多優(yōu)質(zhì)內(nèi)容！

大數(shù)據(jù)?|?Java?|?1024?|?電子書?|?速查表?

Python進階?|?面試?|?手冊?|?成神?|?思想?|?小程序

命令行?|?人工智能?|?軟件測試?|?Web前端?|?Python


掃碼關(guān)注我們
獲取更多學習資料
視頻 |?面試 |?技術(shù) | 電子書?

精通 Spring Boot 系列 07

閱讀全文，約 23?分鐘

Spring Boot 整合持久層開發(fā)

1、ORM

2、Spring Data JPA

2.1 CrudRepository

1）編輯 pom.xml 文件

2）編輯 application.properties 文件

3）創(chuàng)建 User 持久化類

4）創(chuàng)建 UserRepository 數(shù)據(jù)訪問接口

5）創(chuàng)建 UserService 業(yè)務層類

6）創(chuàng)建控制器類

7）創(chuàng)建數(shù)據(jù)庫

8）訪問測試

2.2 PagingAndSortingRepository

1）編輯 pom.xml 文件

與 CrudRepository 接口案例一樣

2）編輯 application.properties 文件

與 CrudRepository 接口案例一樣

3）創(chuàng)建 Article 持久化類

4）定義 ArticleRepository 數(shù)據(jù)訪問接口

5）定義 ArticleService 業(yè)務層類

6）定義 ArticleController 控制器類

7）訪問測試