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Sping Environment为Null的原因和解决方法

2024-08-15 11:54:24   227人阅读

参考:https://github.com/spring-projects/spring-boot/issues/4711 这个issue提出不到20天给我搜出来了,还是相信google的强大

问题: 
在spring的Configuration使用@Bean注册一个BeanFactoryPostProcessor Bean,发现使用@PropertySource,并注入@Resource private Environment env;发现env为null.我调试的大概一个过程,BeanFactoryPostProcessor Bean创建得比较早,创建它之前先创建它的依赖Bean Configuration,而这时发现创建的Configuration的env就是null了.深入的就没去追究了！

解决: 
让此Configuration类实现EnvironmentAware接口,这个接口只有一个void setEnvironment(Environment environment);方法.这里的回调能得到Environment,问题解决!

修改前的代码:

package org.exam.config;import org.exam.service.TestBeanFactoryPostProcessor;import org.exam.service.UserServiceImpl;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.PropertySource;import org.springframework.core.env.Environment;import javax.annotation.Resource;@Configuration@ComponentScan(basePackages = {"org.exam.service"})@PropertySource("classpath:config.properties")public class AppConfigOld {    @Resource    private Environment env;    @Bean    public UserServiceImpl userService(){        System.out.println(env);        return new UserServiceImpl();    }    /*    未加入这个BeanFactoryPostProcessor一切都很正常,一旦加入这个@Bean,env就变为null    @Bean    public TestBeanFactoryPostProcessor testBeanFactoryPostProcessor(){        System.out.println(env);        return new TestBeanFactoryPostProcessor();    }    */}

修改后的代码:

package org.exam.config;import org.exam.service.TestBeanFactoryPostProcessor;import org.exam.service.UserServiceImpl;import org.springframework.context.EnvironmentAware;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.PropertySource;import org.springframework.core.env.Environment;@Configuration@ComponentScan(basePackages = {"org.exam.service"})@PropertySource("classpath:config.properties")public class AppConfig implements EnvironmentAware {    private Environment env;    @Override    public void setEnvironment(Environment environment) {        this.env=environment;    }    @Bean    public UserServiceImpl userService(){        System.out.println(env);        return new UserServiceImpl();    }    @Bean    public TestBeanFactoryPostProcessor testBeanFactoryPostProcessor(){        System.out.println(env);        return new TestBeanFactoryPostProcessor();    }}

值得一提的是:wilkinsona的回答是不建议使用ApplicationContext.虽然可以从ApplicationContext得到Environment,但是这样会在BeanFactoryPostProcessor的创建过程中会引起application context的所有依赖Bean都创建过早,这不是期望的一个结果.

参考:https://github.com/spring-projects/spring-boot/issues/4711 这个issue提出不到20天给我搜出来了,还是相信google的强大

问题: 
在spring的Configuration使用@Bean注册一个BeanFactoryPostProcessor Bean,发现使用@PropertySource,并注入@Resource private Environment env;发现env为null.我调试的大概一个过程,BeanFactoryPostProcessor Bean创建得比较早,创建它之前先创建它的依赖Bean Configuration,而这时发现创建的Configuration的env就是null了.深入的就没去追究了！

解决: 
让此Configuration类实现EnvironmentAware接口,这个接口只有一个void setEnvironment(Environment environment);方法.这里的回调能得到Environment,问题解决!

修改前的代码:

package org.exam.config;import org.exam.service.TestBeanFactoryPostProcessor;import org.exam.service.UserServiceImpl;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.PropertySource;import org.springframework.core.env.Environment;import javax.annotation.Resource;@Configuration@ComponentScan(basePackages = {"org.exam.service"})@PropertySource("classpath:config.properties")public class AppConfigOld {    @Resource    private Environment env;    @Bean    public UserServiceImpl userService(){        System.out.println(env);        return new UserServiceImpl();    }    /*    未加入这个BeanFactoryPostProcessor一切都很正常,一旦加入这个@Bean,env就变为null    @Bean    public TestBeanFactoryPostProcessor testBeanFactoryPostProcessor(){        System.out.println(env);        return new TestBeanFactoryPostProcessor();    }    */}
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修改后的代码:

package org.exam.config;import org.exam.service.TestBeanFactoryPostProcessor;import org.exam.service.UserServiceImpl;import org.springframework.context.EnvironmentAware;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.PropertySource;import org.springframework.core.env.Environment;@Configuration@ComponentScan(basePackages = {"org.exam.service"})@PropertySource("classpath:config.properties")public class AppConfig implements EnvironmentAware {    private Environment env;    @Override    public void setEnvironment(Environment environment) {        this.env=environment;    }    @Bean    public UserServiceImpl userService(){        System.out.println(env);        return new UserServiceImpl();    }    @Bean    public TestBeanFactoryPostProcessor testBeanFactoryPostProcessor(){        System.out.println(env);        return new TestBeanFactoryPostProcessor();    }}
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值得一提的是:wilkinsona的回答是不建议使用ApplicationContext.虽然可以从ApplicationContext得到Environment,但是这样会在BeanFactoryPostProcessor的创建过程中会引起application context的所有依赖Bean都创建过早,这不是期望的一个结果.

Sping Environment为Null的原因和解决方法


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