属性文件之SpringBoot注入

jdbc.properties在resources目录下

　jdbc.driverClassName=com.mysql.jdbc.Driver

jdbc.username=root
jdbc.password=root
jdbc.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8

 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.company</groupId>
    <artifactId>springboot-demo</artifactId>
    <version>1.0.0-SNAPSHOT</version>

    <!--SpringBoot启动器作为父工程-->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.2.RELEASE</version>
    </parent>
    <!--引入web工程启动器-->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.9</version>
        </dependency>
    </dependencies>
</project>

方式一：

　JdbcConfig

　package com.company.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import javax.sql.DataSource;

@Configuration//表明这是一个配置类
@PropertySource("classpath:jdbc.properties")//加载属性文件
public class JdbcConfig {
    @Value("${jdbc.driverClassName}")//从属性文件中取值
    private String driverClassName;
    @Value("${jdbc.username}")
    private String username;
    @Value("${jdbc.password}")
    private String password;
    @Value("${jdbc.url}")
    private String url;

    @Bean//将返回值注入容器
    public DataSource getDataSource(){
        DruidDataSource dataSource=new DruidDataSource();
        dataSource.setDriverClassName(driverClassName);
        dataSource.setUsername(username);
        dataSource.setPassword(password);
        dataSource.setUrl(url);
        return dataSource;
    }
}

方式二：

　　修改jdbc.properties文件名为：application.properties

　　引入Lombok依赖（这一步只是为了简化getter和setter等方法的代码，手动补齐可跳过）

　<dependency>

    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
</dependency>

　　编写属性类JdbcProperties

　package com.company.config;

import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "jdbc")//加载属性文件并指定前缀
@Data//编译期生成getter、setter、equals、hashcode、normal constructor
public class JdbcProperties {
    //成员变量名称必须和属性文件中定义的key前缀.[名称]一致
    private String driverClassName;
    private String username;
    private String password;
    private String url;
}

　　修改JdbcConfig

　　

package com.company.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

@Configuration
@EnableConfigurationProperties(JdbcProperties.class)//启用属性配置类
public class JdbcConfig {

    @Bean
    public DataSource getDataSource(JdbcProperties prop){
        DruidDataSource dataSource=new DruidDataSource();
        dataSource.setDriverClassName(prop.getDriverClassName());
        dataSource.setUsername(prop.getUsername());
        dataSource.setPassword(prop.getPassword());
        dataSource.setUrl(prop.getUrl());
        return dataSource;
    }
}

方式三：

　　删除JdbcProperties类，修改JdbcConfig

　　

package com.company.config;

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

@Configuration
public class JdbcConfig {
    @Bean
    @ConfigurationProperties(prefix = "jdbc")//此时会自动找到application.properties中jdbc为前缀的属性去匹配DruidDataSource中是否有对应的setter方法，自动注入(在DruidDataSource的父类中找到了对应setter方法)

    public DataSource getDataSource(){
        return new DruidDataSource();
    }
}

　　

以上三种方式都可以在controller中注入并debug调试查看属性是否注入成功

package com.company.web;

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 Springboot!";//debug point
    }
}