方式一，实现EnvironmentAware接口
例子：
public class CornerstoneConfiguration implements EnvironmentAware {
private String cornerstoneDomain;
private String staragentHome;
public final String getStaragentHome() {
return staragentHome;
}
public final void setStaragentHome(String staragentHome) {
this.staragentHome = staragentHome;
}
public final String getCornerstoneDomain() {
return cornerstoneDomain;
}
public final void setCornerstoneDomain(String cornerstoneDomain) {
this.cornerstoneDomain = cornerstoneDomain;
}
/**
* 从环境变量中获取配置项值
*/
@Override
public void setEnvironment(Environment environment) {
this.cornerstoneDomain = environment.getProperty("BUC_DOMAIN", "xxx");
this.staragentHome = environment.getProperty("AGENT-HOME", "xxx");
}
}
- 好处：环境变量里没有时可以自己指定默认值，spring启动不会报错
- 缺点：如果你的数据库地址，账号等也从env注入，spring的xml配置里没法这样读取
方式二：借助org.springframework.beans.factory.config.PropertyPlaceholderConfigurer
查看org.springframework.beans.factory.config.PropertyPlaceholderConfigurer源码，发现有个神奇的字段：
private boolean searchSystemEnvironment =
!SpringProperties.getFlag(AbstractEnvironment.IGNORE_GETENV_PROPERTY_NAME);
/**
* Set whether to search for a matching system environment variable
* if no matching system property has been found. Only applied when
* "systemPropertyMode" is active (i.e. "fallback" or "override"), right
* after checking JVM system properties.
* <p>Default is "true". Switch this setting off to never resolve placeholders
* against system environment variables. Note that it is generally recommended
* to pass external values in as JVM system properties: This can easily be
* achieved in a startup script, even for existing environment variables.
* <p><b>NOTE:</b> Access to environment variables does not work on the
* Sun VM 1.4, where the corresponding {@link System#getenv} support was
* disabled - before it eventually got re-enabled for the Sun VM 1.5.
* Please upgrade to 1.5 (or higher) if you intend to rely on the
* environment variable support.
* @see #setSystemPropertiesMode
* @see java.lang.System#getProperty(String)
* @see java.lang.System#getenv(String)
*/
public void setSearchSystemEnvironment(boolean searchSystemEnvironment) {
this.searchSystemEnvironment = searchSystemEnvironment;
}
protected String resolveSystemProperty(String key) {
try {
String value = System.getProperty(key);
// 哈哈哈哈哈，我喜欢这个
if (value == null && this.searchSystemEnvironment) {
value = System.getenv(key);
}
return value;
}
catch (Throwable ex) {
if (logger.isDebugEnabled()) {
logger.debug("Could not access system property '" + key + "': " + ex);
}
return null;
}
}
呵呵哒，他有自己设定默认值，不用管，反正我直接用setter注入一个true给它，哇嘎嘎。。。
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:app-config.properties</value>
<value>classpath:application.properties</value>
</list>
</property>
<property name="searchSystemEnvironment" value="true" />
</bean>
- 这样之后，在spring的任何bean里面都可以@Value("${xxx}")的形式注入啦(不过注意哦，不存在的话spring会直接启动报错的哟)
- xml里面也可以直接引。。
