01_SpringBoot 入门案例

张创琦 2022.03.10

相关配置看文件说明。此处只展示代码和运行结果。

目录结构

pom.xml

<?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>com.lxs</groupId>
    <artifactId>spring-boot-demo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <!-- 添加父坐标工程 -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.10</version>
        </dependency>
    </dependencies>
</project>

application.properties （原名：jdbc.properties）

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/ssm1
jdbc.username=root
jdbc.password=123456

Application.java

package com.lxs;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

HelloController.java

package com.lxs.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.sql.DataSource;
@RestController
public class HelloController {
    @Autowired
    private DataSource dataSource;
    @GetMapping("/hello")
    public String hello(){
        return "hello, spring boot! " + dataSource;
    }
}

JdbcConfig.java

方法1： 通过value注解

package com.lxs.config;
import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
// 注意这里的包是sql的！！！
import javax.management.MXBean;
import javax.sql.DataSource;
@Configuration
@PropertySource("classpath:application.properties")
public class JdbcConfig {
    @Value("${jdbc.url}")
    String url;
    @Value("${jdbc.driverClassName}")
    String driverClassName;
    @Value("${jdbc.username}")
    String username;
    @Value("${jdbc.password}")
    String password;
    @Bean
    public DataSource dataSource(){
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setUrl(url);
        dataSource.setDriverClassName(driverClassName);
        dataSource.setUsername(username);
        dataSource.setPassword(password);
        return dataSource;
    }
}

方法2： 通过EnableConfigurationProperties注解

package com.lxs.config;
import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
// 注意这里的包是sql的！！！
import javax.management.MXBean;
import javax.sql.DataSource;
@Configuration
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfig {
    @Bean
    public DataSource dataSource(JdbcProperties jdbc){
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setUrl(jdbc.getUrl());
        dataSource.setDriverClassName(jdbc.getDriverClassName());
        dataSource.setUsername(jdbc.getUsername());
        dataSource.setPassword(jdbc.getPassword());
        return dataSource;
    }
}

运行结果展示

Tomcat initialized with port(s): 8080 (http)
Servlet dispatcherServlet mapped to [/]
Mapped "{[/hello],methods=[GET]}" onto public java.lang.String com.lxs.controller.HelloController.hello()

debug相关结果展示：

松散绑定

（未调试，记得调试）

举例：

可以将application.properties中的驼峰命名方式转换，

比如将 jdbc.driver_class_name 在 jdbcConfig 中可以转换为 jdbc.driverClassName 。

更优雅的注入

比如：删掉 JdbcProperties

JdbcConfig.java

package com.lxs.config;
import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
// 注意这里的包是sql的！！！
import javax.management.MXBean;
import javax.sql.DataSource;
@Configuration
public class JdbcConfig {
    // 自动将同名属性配置，高科技！
    @Bean
    public DataSource dataSource(){
        DruidDataSource dataSource = new DruidDataSource();
        return dataSource;
    }
}