Spring Boot的数据访问之Spring Boot + jpa的demo

分手后的思念是犯贱 2021-12-22 19:41 325阅读 0赞

**1. 快速地创建一个项目，pom中选择如下**

<?xml version="1.0" encoding="UTF-8"?>
    <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>4.0.0</modelVersion>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.3.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <groupId>com.example</groupId>
        <artifactId>demo</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>demo</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
        </properties>
    
        <dependencies>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter</artifactId>
            </dependency>
    
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>
    
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    
    </project>

**2. 新建一个实体，这边以Book对象为例，主要囊括了书店中书的一些信息**

**![1064427-20190312112506363-208792454.png][]**

package com.example.demo.entity;
    
    
    import javax.persistence.Column;
    import javax.persistence.Entity;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Id;
    import java.io.Serializable;
    
    @Entity
    public class Book implements Serializable {
    
        public static final long seriaVersionUID = 1L;
        
        @Id
        @GeneratedValue
        private long id;
    
        @Column(nullable=false,unique=true)
        private String name;
    
        @Column(nullable=false)
        private String author;
    
        @Column(nullable=false)
        private String ontime;
    
        @Column(nullable=false)
        private int number;
    
        @Column(nullable=false)
        private float price;
    
        @Column(nullable=false)
        private String createdt;
        @Column(nullable=false)
        private String updatedt;
        @Column(nullable=false)
        private String creatuid;
        @Column(nullable=false)
        private String updateuid;
    
        public long getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getAuthor() {
            return author;
        }
    
        public void setAuthor(String author) {
            this.author = author;
        }
    
        public String getOntime() {
            return ontime;
        }
    
        public void setOntime(String ontime) {
            this.ontime = ontime;
        }
    
        public int getNumber() {
            return number;
        }
    
        public void setNumber(int number) {
            this.number = number;
        }
    
        public float getPrice() {
            return price;
        }
    
        public void setPrice(float price) {
            this.price = price;
        }
    
        public String getCreatedt() {
            return createdt;
        }
    
        public void setCreatedt(String createdt) {
            this.createdt = createdt;
        }
    
        public String getUpdatedt() {
            return updatedt;
        }
    
        public void setUpdatedt(String updatedt) {
            this.updatedt = updatedt;
        }
    
        public String getCreatuid() {
            return creatuid;
        }
    
        public void setCreatuid(String creatuid) {
            this.creatuid = creatuid;
        }
    
        public String getUpdateuid() {
            return updateuid;
        }
    
        public void setUpdateuid(String updateuid) {
            this.updateuid = updateuid;
        }
    
        protected Book(){super();};
    
        public Book(String name, String author, String ontime, int number, float price, String createdt, String updatedt, String creatuid, String updateuid) {
            this.name = name;
            this.author = author;
            this.ontime = ontime;
            this.number = number;
            this.price = price;
            this.createdt = createdt;
            this.updatedt = updatedt;
            this.creatuid = creatuid;
            this.updateuid = updateuid;
        }
    
        @Override
        public String toString() {
            return "Book{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", author='" + author + '\'' +
                    ", ontime='" + ontime + '\'' +
                    ", number=" + number +
                    ", price=" + price +
                    ", createdt='" + createdt + '\'' +
                    ", updatedt='" + updatedt + '\'' +
                    ", creatuid='" + creatuid + '\'' +
                    ", updateuid='" + updateuid + '\'' +
                    '}';
        }
    }

**3. 新建一个BookRepository接口，且继承JpaRepository**

public interface BookRepository extends JpaRepository<Book, Long> {
    
        
    }

**4. 了解hibernate的ddl-auto四种模式和用途**

# 服务端口
    server.port=8083
    
    spring.datasource.url=jdbc:mysql://127.0.0.1:3306/spring
    spring.datasource.username=root
    spring.datasource.password=root
    spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
    
    spring.jpa.hibernate.ddl-auto=validate

spring.jpa.hibernate.ddl-auto = 可以是4中Value
    create
    create-drop
    validate
    update

![1064427-20190312113150177-1440300430.png][]

Hibernate我们公司的正式项目中基本不用，原因是性能上不是很好，不知道其他公司使用起来如何？

hibernate在多线程下，拼接sql，知道数据库有问题，却很难定位到是哪一段sql。后来渐渐弃用。用mybaits了~

**5. 添加controller进行新增数据**

package com.example.demo.controller;
    
    
    import com.example.demo.entity.Book;
    import com.example.demo.entity.BookRepository;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseBody;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.List;
    
    @RestController
    public class BookController {
    
        @Autowired
        private BookRepository bookRepository;
    
    
        @RequestMapping("/save")
        @ResponseBody
        public void save() {
            bookRepository.save(new Book("书名11", "作者", "上架时间", 100, 23, "创建时间", "更新时间", "创建uid", "更新uid"));
            bookRepository.save(new Book("书名12", "作者", "20001111", 100, 23, "19990111", "19990111", "3", "4"));
            bookRepository.save(new Book("西游记10", "吴承恩", "19991211", 100, 20, "19991111", "19991111", "2", "3"));
        } }

项目启动起来，在浏览器中输入 http://localhost:8083/save，查询数据库中，已经新增了三条记录；

可以顺带测试下ddl-auto的四种值，是否有如同描述一般的作用

![1064427-20190312120603579-935196081.png][]

**6. 再添加查询方法，并在controller中进行查询**

package com.example.demo.entity;
    
    import org.springframework.data.jpa.repository.JpaRepository;
    
    import java.util.List;
    
    public interface BookRepository extends JpaRepository<Book, Long> {
    
        List<Book> findByAuthor(String author);
    }

再在BookRepository 中添加查找方法，根据作者查询出符合的Book 列表

package com.example.demo.controller;
    
    import com.example.demo.entity.Book;
    import com.example.demo.entity.BookRepository;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.List;
    
    @RestController
    public class BookController {
    
        @Autowired
        private BookRepository bookRepository;
    
    
        @RequestMapping("/save")
        public void save() {
            bookRepository.save(new Book("书名11", "作者", "上架时间", 100, 23, "创建时间", "更新时间", "创建uid", "更新uid"));
            bookRepository.save(new Book("书名12", "作者", "20001111", 100, 23, "19990111", "19990111", "3", "4"));
            bookRepository.save(new Book("西游记10", "吴承恩", "19991211", 100, 20, "19991111", "19991111", "2", "3"));
        }
    
        @RequestMapping("/findByAuthor")
        public void findByAuthor() {
            List<Book> result = bookRepository.findByAuthor("作者");
            System.out.println("一共有多少条呢----" + result.size());
            for (Book book : result) {
                System.out.println(book);
            }
            System.out.println("================================");
        }
    }

保存，启动新项目，在浏览器中输入http://localhost:8083/findByAuthor，查看控制台是否打印出Book信息

![1064427-20190312113941543-1535373149.png][]

转载于:https://www.cnblogs.com/qianjinyan/p/10515528.html

[1064427-20190312112506363-208792454.png]: /images/20211220/f6ed88bb5c3a4dbcbdd10f68c8196774.png
[1064427-20190312113150177-1440300430.png]: /images/20211220/d2d4a229085f411397abb43886c634c3.png
[1064427-20190312120603579-935196081.png]: /images/20211220/e77eedc00f9548c88b3ccfd6a1665139.png
[1064427-20190312113941543-1535373149.png]: /images/20211220/2d95442c3e42436ca88b6521a2fa2b7c.png