上篇文章介绍了Spring源码中的三步中的super(parent)的代码,本文介绍下setConfigLocations(configLocation)方法
类图
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {
// 1.初始化父类
super(parent);
// 2.设置本地的配置信息
setConfigLocations(configLocations);
// 3.完成Spring容器的初始化
if (refresh) {
refresh();
}
}
public void setConfigLocations(String... locations) {
if (locations != null) {
Assert.noNullElements(locations, "Config locations must not be null");
this.configLocations = new String[locations.length];
for (int i = 0; i < locations.length; i++) {
//循环取出每一个path参数,在此处就一个“applicationContext.xml“”
this.configLocations[i] = resolvePath(locations[i]).trim();
}
}
else {
this.configLocations = null;
}
}
// 这个方法的目的是替换掉path字符串中的占位符${XXX}这样的内容
protected String resolvePath(String path) {
// 1.进入getEnvironment()
// 2.进入resolveRequiredPlaceholders方法
return getEnvironment().resolveRequiredPlaceholders(path);
}
getEnvironment():创建了ConfigurableEnvironment 对象
public ConfigurableEnvironment getEnvironment() {
if (this.environment == null) {
this.environment = createEnvironment();
}
return this.environment;
}
提供的方法中可以看出两个功能
resolveRequiredPlaceholders(path)
处理占位符的方法
@Override
public String resolveRequiredPlaceholders(String text) throws IllegalArgumentException {
if (this.strictHelper == null) {
// 创建PropertyPlaceholderHelper对象
this.strictHelper = createPlaceholderHelper(false);
}
return doResolvePlaceholders(text, this.strictHelper);
}
进入doResolvePlaceholders继续查看
private String doResolvePlaceholders(String text, PropertyPlaceholderHelper helper) {
return helper.replacePlaceholders(text, new PropertyPlaceholderHelper.PlaceholderResolver() {
@Override
public String resolvePlaceholder(String placeholderName) {
//
return getPropertyAsRawString(placeholderName);
}
});
}
getPropertyAsRawString的具体实现在PropertySourcesPropertyResolver类中
@Override
protected String getPropertyAsRawString(String key) {
return getProperty(key, String.class, false);
}
继续跟踪helper.replacePlaceholders(),到了PropertyPlaceholderHelper.parseStringValue方法,这里面逐一找出每个占位符去做替换:
public String replacePlaceholders(String value, PlaceholderResolver placeholderResolver) {
Assert.notNull(value, "'value' must not be null");
return parseStringValue(value, placeholderResolver, new HashSet<String>());
}
parseStringValue方法中,找到了占位符后,会调用入参placeholderResolver的resolvePlaceholder(placeholder)方法,也就是上面匿名类的getPropertyAsRawString方法(实际上就是PropertySourcesPropertyResolver.getPropertyAsRawString方法),最终会在PropertySourcesPropertyResolver.getProperty方法中找出所有的属性来匹配占位符
protected String parseStringValue(
String strVal, PlaceholderResolver placeholderResolver, Set<String> visitedPlaceholders) {
StringBuilder result = new StringBuilder(strVal);
int startIndex = strVal.indexOf(this.placeholderPrefix);
while (startIndex != -1) {
int endIndex = findPlaceholderEndIndex(result, startIndex);
if (endIndex != -1) {
String placeholder = result.substring(startIndex + this.placeholderPrefix.length(), endIndex);
String originalPlaceholder = placeholder;
if (!visitedPlaceholders.add(originalPlaceholder)) {
throw new IllegalArgumentException(
"Circular placeholder reference '" + originalPlaceholder + "' in property definitions");
}
// Recursive invocation, parsing placeholders contained in the placeholder key.
placeholder = parseStringValue(placeholder, placeholderResolver, visitedPlaceholders);
// Now obtain the value for the fully resolved key...
String propVal = placeholderResolver.resolvePlaceholder(placeholder);
if (propVal == null && this.valueSeparator != null) {
int separatorIndex = placeholder.indexOf(this.valueSeparator);
if (separatorIndex != -1) {
String actualPlaceholder = placeholder.substring(0, separatorIndex);
String defaultValue = placeholder.substring(separatorIndex + this.valueSeparator.length());
propVal = placeholderResolver.resolvePlaceholder(actualPlaceholder);
if (propVal == null) {
propVal = defaultValue;
}
}
}
if (propVal != null) {
// Recursive invocation, parsing placeholders contained in the
// previously resolved placeholder value.
propVal = parseStringValue(propVal, placeholderResolver, visitedPlaceholders);
result.replace(startIndex, endIndex + this.placeholderSuffix.length(), propVal);
if (logger.isTraceEnabled()) {
logger.trace("Resolved placeholder '" + placeholder + "'");
}
startIndex = result.indexOf(this.placeholderPrefix, startIndex + propVal.length());
}
else if (this.ignoreUnresolvablePlaceholders) {
// Proceed with unprocessed value.
startIndex = result.indexOf(this.placeholderPrefix, endIndex + this.placeholderSuffix.length());
}
else {
throw new IllegalArgumentException("Could not resolve placeholder '" +
placeholder + "'" + " in string value \"" + strVal + "\"");
}
visitedPlaceholders.remove(originalPlaceholder);
}
else {
startIndex = -1;
}
}
return result.toString();
}
名称 | 作用 |
---|---|
ConfigurableEnvironment | 1.创建PropertyResolver;2.向PropertyResolver提供环境变量、 Java进程变量 |
PropertyResolver | 1.创建PropertyPlaceholderHelper;2.定义占位符的前缀和后缀(placeholderPrefix、placeholderSuffix);3.提供getPropertyAsRawString方法给PropertyPlaceholderHelper调用,用来获取指定key对应的环境变量; |
PropertyPlaceholderHelper | 1.找到字符串中的占位符;2.调用PropertyResolver.getPropertyAsRawString方法,从环境变量中取出占位符对应的值3.用环境变量的值替换占位符; |
至此setConfigLocations的代码就查看到此,后面介绍refresh的代码