Spring-MessageSource

docs/Spring/clazz/Spring-MessageSource.md

@@ -0,0 +1,210 @@
+# Spring MessageSource
+- Author: [HuiFer](https://github.com/huifer)
+- 源码阅读仓库: [huifer-spring](https://github.com/huifer/spring-framework-read)
+
+## 初始化入口
+- `org.springframework.context.support.AbstractApplicationContext.refresh`方法有`initMessageSource()`方法进行了`MessageSource`初始化
+
+
+
+```java
+    protected void initMessageSource() {
+        ConfigurableListableBeanFactory beanFactory = getBeanFactory();
+        // 判断是否含有 messageSource
+        if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
+            // 读取xml配置文件中 id="messageSource"的数据
+            this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
+            // Make MessageSource aware of parent MessageSource.
+            if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
+                HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
+                if (hms.getParentMessageSource() == null) {
+                    // Only set parent context as parent MessageSource if no parent MessageSource
+                    // registered already.
+                    hms.setParentMessageSource(getInternalParentMessageSource());
+                }
+            }
+            if (logger.isTraceEnabled()) {
+                logger.trace("Using MessageSource [" + this.messageSource + "]");
+            }
+        }
+        else {
+            // Use empty MessageSource to be able to accept getMessage calls.
+            // 没有使用默认的 DelegatingMessageSource
+            DelegatingMessageSource dms = new DelegatingMessageSource();
+            dms.setParentMessageSource(getInternalParentMessageSource());
+            this.messageSource = dms;
+            // 注册单例对象
+            beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
+            if (logger.isTraceEnabled()) {
+                logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
+            }
+        }
+    }
+
+```
+
+
+
+
+
+读取xml配置文件
+
+![image-20200119141937915](/images/spring/image-20200119141937915.png)
+
+
+
+
+
+
+
+## getMessage
+
+- `org.springframework.context.support.AbstractApplicationContext#getMessage(java.lang.String, java.lang.Object[], java.util.Locale)`
+
+```java
+    @Override
+    public String getMessage(String code, @Nullable Object[] args, Locale locale) throws NoSuchMessageException {
+        return getMessageSource().getMessage(code, args, locale);
+    }
+
+```
+
+- `org.springframework.context.support.AbstractMessageSource#getMessage(java.lang.String, java.lang.Object[], java.util.Locale)`
+
+  ```java
+      @Override
+      public final String getMessage(String code, @Nullable Object[] args, Locale locale) throws NoSuchMessageException {
+          // 获取对应的信息
+          String msg = getMessageInternal(code, args, locale);
+          if (msg != null) {
+              return msg;
+          }
+          // 默认信息 null
+          String fallback = getDefaultMessage(code);
+          if (fallback != null) {
+              return fallback;
+          }
+          throw new NoSuchMessageException(code, locale);
+      }
+  
+  ```
+
+  - 两个方法
+
+    1. `org.springframework.context.support.AbstractMessageSource#getDefaultMessage(java.lang.String)`
+
+       ```java
+           @Nullable
+           protected String getDefaultMessage(String code) {
+               // 判断是否使用默认值
+               if (isUseCodeAsDefaultMessage()) {
+                   return code;
+               }
+               return null;
+           }
+       
+       ```
+
+       - 返回code本身或者`null`
+
+    2. `org.springframework.context.support.AbstractMessageSource#getMessageInternal`
+
+       ```JAVA
+           @Nullable
+           protected String getMessageInternal(@Nullable String code, @Nullable Object[] args, @Nullable Locale locale) {
+               if (code == null) {
+                   return null;
+               }
+               if (locale == null) {
+                   // 获取语言默认值
+                   locale = Locale.getDefault();
+               }
+               Object[] argsToUse = args;
+       
+               if (!isAlwaysUseMessageFormat() && ObjectUtils.isEmpty(args)) {
+                   // Optimized resolution: no arguments to apply,
+                   // therefore no MessageFormat needs to be involved.
+                   // Note that the default implementation still uses MessageFormat;
+                   // this can be overridden in specific subclasses.
+                   String message = resolveCodeWithoutArguments(code, locale);
+                   if (message != null) {
+                       return message;
+                   }
+               }
+       
+               else {
+                   // Resolve arguments eagerly, for the case where the message
+                   // is defined in a parent MessageSource but resolvable arguments
+                   // are defined in the child MessageSource.
+                   argsToUse = resolveArguments(args, locale);
+       
+                   MessageFormat messageFormat = resolveCode(code, locale);
+                   if (messageFormat != null) {
+                       synchronized (messageFormat) {
+                           return messageFormat.format(argsToUse);
+                       }
+                   }
+               }
+       
+               // Check locale-independent common messages for the given message code.
+               Properties commonMessages = getCommonMessages();
+               if (commonMessages != null) {
+                   String commonMessage = commonMessages.getProperty(code);
+                   if (commonMessage != null) {
+                       return formatMessage(commonMessage, args, locale);
+                   }
+               }
+       
+               // Not found -> check parent, if any.
+               return getMessageFromParent(code, argsToUse, locale);
+           }
+       
+       ```
+
+       
+
+- `org.springframework.context.support.ResourceBundleMessageSource#resolveCodeWithoutArguments`
+
+  ```JAVA
+      @Override
+      protected String resolveCodeWithoutArguments(String code, Locale locale) {
+          Set<String> basenames = getBasenameSet();
+          for (String basename : basenames) {
+              // 加载 basename
+              ResourceBundle bundle = getResourceBundle(basename, locale);
+              if (bundle != null) {
+                  // 从basename对应的文件中获取对应的值
+                  String result = getStringOrNull(bundle, code);
+                  if (result != null) {
+                      return result;
+                  }
+              }
+          }
+          return null;
+      }
+  
+  ```
+
+  
+
+
+
+
+
+![image-20200119143046066](/images/spring/image-20200119143046066.png)
+
+
+
+- 加载后截图
+
+  获取方法`String result = getStringOrNull(bundle, code);`就是map获取
+
+![image-20200119144019171](/images/spring/image-20200119144019171.png)
+
+
+
+
+
+- 没有配置文件的情况
+
+  ![image-20200119145138205](/images/spring/image-20200119145138205.png)