springboot中普通JAVA类读取application.yml配置项

关键点：
需要将类纳入SPRING管理，在类上增加@Componet注解
在类中使用@Value指定默认的application.yml文件对应的节点名称
使用时需要使用@Autowried注入

可能的报错
org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type ‘com.***.***.ConfigBean’ available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.ann

或是 报 NULL对象指针异常。

原因：启动类所在包未引入@ComponentScan扫描。

application.yml内容:

spring:
datasource:
# oracle
url: jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.1.15)(PORT=1521))) (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=okok)))
username: xiawu
password: xxxbbbccc
driver-class-name: oracle.jdbc.driver.OracleDriver
platform: oracle

ConfigBean.java内容：

package com.bbb;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
public class ConfigBean {
@Value("${spring.datasource.url}")
private String dbUrl;

@Value("${spring.datasource.username}")
private String dbUser;

@Value("${spring.datasource.password}")
private String dbPwd;

@Value("${spring.datasource.driver-class-name}")
private String dbDriver;


public String getDbUrl() {
    return dbUrl;
}

public void setDbUrl(String dbUrl) {
    this.dbUrl = dbUrl;
}

public String getDbUser() {
    return dbUser;
}

public void setDbUser(String dbUser) {
    this.dbUser = dbUser;
}

public String getDbPwd() {
    return dbPwd;
}

public void setDbPwd(String dbPwd) {
    this.dbPwd = dbPwd;
}

public String getDbDriver() {
    return dbDriver;
}

public void setDbDriver(String dbDriver) {
    this.dbDriver = dbDriver;
}

}

启动类：

假定ConfigBean在com.bbb包下
@ComponentScan (basePackages = {“com.bbb”})

测试类（受Spring管理的类，比如在某个Controller中）：

测试类中注入配置类
@Autowired
private ConfigBean configBean;
使用
configBean.getDbUrl();

说明：以上测试类也要属于SPING管理才可以正常调用，否则ConfigBean对象会报空指 针异常。

如果要在非SPRING管理的类中调用，需要先获取到SPRING的ApplicationContext对象，根据该对象中的bean去获取具体配置文件的参数。以下是代码：

---

获取ApplicationContext对象的工具类：

import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class ApplicationContextUtil implements ApplicationContextAware {
private static org.springframework.context.ApplicationContext applicationContext;

public static org.springframework.context.ApplicationContext getApplicationContext() {
    return applicationContext;
}

public  void setApplicationContext(org.springframework.context.ApplicationContext context){
    applicationContext = context;
}

}

非SPRING管理的普通类中的调用代码：

ApplicationContext app= ApplicationContextUtil.getApplicationContext();
ConfigBean configBean = app.getBean(ConfigBean.class);
System.out.println("========="+configBean.getDbUrl());