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IDEA中便捷内存数据库H2的最简使用方式

岁月已走远 人气:0

  在IDEA中有时候为了练习,需要使用到数据库,但如果自己工作或开发机子上本来没有安装数据库,也没有可用的远程数据库时,我们可以直接在IDEA环境上使用便捷式的内存数据库H2,关于H2更多知识就自己去找一下了,接下来讲一下如何在IDEA下的Spring Boot项目中把它用起来!

  首先新建一个空的Maven项目,编辑项目pom.xml文件,增加Spring Boot和最基础的数据访问相关jar包依赖:

<?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>

    <groupId>org.example</groupId>
    <artifactId>microservice-simple-provider-user</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <parent>
        <artifactId>spring-boot-starter-parent</artifactId>
        <groupId>org.springframework.boot</groupId>
        <version>2.4.2</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <!--SpringBoot的Web项目起步依赖-->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.4.2</version>
        </dependency>
        <dependency>
            <!--SpringBoot的jpa数据访问组件起步依赖-->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <version>2.3.1.RELEASE</version>
        </dependency>
        <dependency>
            <!--自动构建H2嵌入式或内存数据库依依赖-->
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.200</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>2.4.2</version>
            </plugin>
        </plugins>
    </build>
</project>

 

  在classpath路径范围内增加建表SQL脚本文件和数据初始化文件:

 

 

 

  再添加Spring Boot项目配置文件application.yml

 

  再为项目添加一个Spring Boot启动类,即可将应用跑起来,并进行H2内存数据库的连接了:

 

  最后,我们来为项目做一个最简单的H2内存数据库的使用样例,为H2中的User表增加对应的实体类User.java、基于JPA的数据访问对象UserRepository.java和接口层类UserController.java:

User.java类:

package com.example.models;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

import javax.persistence.*;
import java.math.BigDecimal;

@JsonIgnoreProperties(value = {"hibernateLazyInitializer"})
@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column
    private String username;

    @Column
    private String name;

    @Column
    private Integer age;

    @Column
    private BigDecimal balance;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public BigDecimal getBalance() {
        return balance;
    }

    public void setBalance(BigDecimal balance) {
        this.balance = balance;
    }
}

UserRepository.java类:

package com.example.dao;

import com.example.models.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
}

UserController.java类:

package com.example.controller;

import com.example.dao.UserRepository;
import com.example.models.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {
    @Autowired
    private UserRepository userRepository;

    @GetMapping("/{id}")
    public User findById(@PathVariable Long id) {
        User oneUser = this.userRepository.getOne(id);
        return oneUser;
    }
}

 

  最后的项目结构如图所示:

 

  最后来看一下效果:

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