访问H2数据库的SpringBoot工程

JDK：1.8.0_212

IDE：STS4（Spring Tool Suit4 Version: 4.3.2.RELEASE）

工程下载：https://files.cnblogs.com/files/xiandedanteng/RestTeamplate20190929.rar

工程还是使用Spring Starter project创建，添加Web依赖，之后在pom.xml添加JPA和H2的依赖。

<?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 https://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>2.1.8.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.hy</groupId>
    <artifactId>RestTeamplate</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>RestTeamplate</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-web</artifactId>
        </dependency>
        
        <!-- Spring Data JPA依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        
        <!-- 嵌入式数据库H2依赖 -->
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

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

</project>

在src/main/resources下添加文件schema.sql

drop table emp if exists;
create table emp(id bigint generated by default as identity,name varchar(30),primary key(id));

在src/main/resources下添加文件data.sql

insert into emp(id,name) values (1,'孟郊andy');
insert into emp(id,name) values (2,'bill');
insert into emp(id,name) values (3,'cindy');
insert into emp(id,name) values (4,'douglas');

改写配置文件application.properties如下：

server.port=8080
spring.jpa.generate-ddl=false
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=none
spring.datasource.platform=h2
spring.datasource.schema=classpath:schema.sql
spring.datasource.data=classpath:data.sql

然后是实体类：

package com.example.demo;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Emp {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private long id;
    
    @Column
    private String name;

    public long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

DAO：

package com.example.demo;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface EmpRepo extends JpaRepository<Emp,Long>{

}

控制器：

package com.example.demo;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class Ctrl {
    @Autowired
    private EmpRepo empRepo;
    
    @RequestMapping("/test")
    public String test() {
        return "你好";
    }
    
    @RequestMapping("/emp/{id}")
    public Object findById(@PathVariable Long id) {
        Emp e=null;
        
        Optional<Emp> opt =this.empRepo.findById(id);
        if(opt.isPresent()) {
            e=opt.get();
        }
        
        return e;
    }
}