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source-code-hunter/docs/Spring/mvc/Spring-MVC-HandlerMapping.md

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# Spring HandlerMapping
- Author: [HuiFer](https://github.com/huifer)
- 源码阅读仓库: [SourceHot-spring](https://github.com/SourceHot/spring-framework-read)
- 源码路径: `org.springframework.jms.annotation.EnableJms`
- `org.springframework.web.servlet.HandlerMapping`
- HandlerMapping 处理映射关系, 通过请求转换成对象`HandlerExecutionChain`
```java
public interface HandlerMapping {
HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
// 其他静态变量省略
}
```
![image](/images/springMVC/HandlerMapping.png)
```java
@Override
@Nullable
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
// 转换成handler
Object handler = getHandlerInternal(request);
if (handler == null) {
// 获取默认的 handler
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
// handler 是beanName 直接从容器中获取
String handlerName = (String) handler;
handler = obtainApplicationContext().getBean(handlerName);
}
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
if (logger.isTraceEnabled()) {
logger.trace("Mapped to " + handler);
}
else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
logger.debug("Mapped to " + executionChain.getHandler());
}
if (hasCorsConfigurationSource(handler) || CorsUtils.isPreFlightRequest(request)) {
CorsConfiguration config = (this.corsConfigurationSource != null ? this.corsConfigurationSource.getCorsConfiguration(request) : null);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
config = (config != null ? config.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}
```
- `getHandlerInternal`方法是一个抽象方法
```JAVA
@Nullable
protected abstract Object getHandlerInternal(HttpServletRequest request) throws Exception;
```
存在的实现方法
![image-20200915135933146](images/image-20200915135933146.png)
- 先看`org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#getHandlerInternal`方法是怎么一回事.
```java
@Override
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
// 获取当前请求路径
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
// 设置属性
request.setAttribute(LOOKUP_PATH, lookupPath);
// 上锁
this.mappingRegistry.acquireReadLock();
try {
// 寻找 handler method
HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
}
finally {
// 释放锁
this.mappingRegistry.releaseReadLock();
}
}
```
## UrlPathHelper
- 全路径:`org.springframework.web.util.UrlPathHelper`
- 几个属性
```java
/**
* 是否全路径标记
*/
private boolean alwaysUseFullPath = false;
/**
* 是否需要 decode
*/
private boolean urlDecode = true;
private boolean removeSemicolonContent = true;
/**
* 默认的encoding编码格式
*/
private String defaultEncoding = WebUtils.DEFAULT_CHARACTER_ENCODING;
```
### getPathWithinApplication
```java
public String getPathWithinApplication(HttpServletRequest request) {
// 获取 context path
String contextPath = getContextPath(request);
// 获取 uri
String requestUri = getRequestUri(request);
String path = getRemainingPath(requestUri, contextPath, true);
if (path != null) {
// Normal case: URI contains context path.
return (StringUtils.hasText(path) ? path : "/");
}
else {
return requestUri;
}
}
```
1. 从 request 中获取 context-path
1. 从属性中直接获取
2. 从 request 中调用 getContextPath 获取
3. 判断是否是**`/`**
4. decode request string
2. 从 request 中虎丘 request-uri
1. 从属性中获取
2. 从 request 中调用 getRequestURI 获取
3. decode
3. 获取剩余路径
### getContextPath
- 获取 context-path 地址
```java
public String getContextPath(HttpServletRequest request) {
// 从 request 获取 context path
String contextPath = (String) request.getAttribute(WebUtils.INCLUDE_CONTEXT_PATH_ATTRIBUTE);
if (contextPath == null) {
contextPath = request.getContextPath();
}
if ("/".equals(contextPath)) {
// Invalid case, but happens for includes on Jetty: silently adapt it.
contextPath = "";
}
// decode context path
return decodeRequestString(request, contextPath);
}
```
### decodeRequestString
- 判断是否需要编码, 需要编码就做编码操作,不需要就直接返回
```java
public String decodeRequestString(HttpServletRequest request, String source) {
// 判断是否需要编码
if (this.urlDecode) {
// 进行编码
return decodeInternal(request, source);
}
return source;
}
```
### decodeInternal
- 编码方法
```java
@SuppressWarnings("deprecation")
private String decodeInternal(HttpServletRequest request, String source) {
// 确定编码方式
String enc = determineEncoding(request);
try {
// 将 source 编译成 enc 的编码方式
return UriUtils.decode(source, enc);
}
catch (UnsupportedCharsetException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Could not decode request string [" + source + "] with encoding '" + enc +
"': falling back to platform default encoding; exception message: " + ex.getMessage());
}
// 直接编码,JDK底层编码
return URLDecoder.decode(source);
}
}
```
### determineEncoding
- 确认编码
```java
protected String determineEncoding(HttpServletRequest request) {
// 从 request 中获取编码方式
String enc = request.getCharacterEncoding();
if (enc == null) {
// 默认编码
enc = getDefaultEncoding();
}
return enc;
}
```
### getRequestUri
- 获取 uri 地址
```java
public String getRequestUri(HttpServletRequest request) {
// 从属性中获取
String uri = (String) request.getAttribute(WebUtils.INCLUDE_REQUEST_URI_ATTRIBUTE);
if (uri == null) {
// 调用方法获取
uri = request.getRequestURI();
}
//编码和清理数据
return decodeAndCleanUriString(request, uri);
}
```
### decodeAndCleanUriString
- 编码和清理数据
```java
private String decodeAndCleanUriString(HttpServletRequest request, String uri) {
// 去掉分号
uri = removeSemicolonContent(uri);
// decoding
uri = decodeRequestString(request, uri);
// 去掉 // 双斜杠
uri = getSanitizedPath(uri);
return uri;
}
```
### shouldRemoveTrailingServletPathSlash
- 是否删除 servlet path 后的斜杠
- 默认是 false .
- 代码流程
1. 通过 classLoader 加载 `"com.ibm.ws.webcontainer.WebContainer"`
2. 调用方法 `"getWebContainerProperties"`
3. 从方法结果中取`"getWebContainerProperties"`
```java
private boolean shouldRemoveTrailingServletPathSlash(HttpServletRequest request) {
if (request.getAttribute(WEBSPHERE_URI_ATTRIBUTE) == null) {
// Regular servlet container: behaves as expected in any case,
// so the trailing slash is the result of a "/" url-pattern mapping.
// Don't remove that slash.
return false;
}
Boolean flagToUse = websphereComplianceFlag;
if (flagToUse == null) {
ClassLoader classLoader = UrlPathHelper.class.getClassLoader();
String className = "com.ibm.ws.webcontainer.WebContainer";
String methodName = "getWebContainerProperties";
String propName = "com.ibm.ws.webcontainer.removetrailingservletpathslash";
boolean flag = false;
try {
Class<?> cl = classLoader.loadClass(className);
Properties prop = (Properties) cl.getMethod(methodName).invoke(null);
flag = Boolean.parseBoolean(prop.getProperty(propName));
}
catch (Throwable ex) {
if (logger.isDebugEnabled()) {
logger.debug("Could not introspect WebSphere web container properties: " + ex);
}
}
flagToUse = flag;
websphereComplianceFlag = flag;
}
// Don't bother if WebSphere is configured to be fully Servlet compliant.
// However, if it is not compliant, do remove the improper trailing slash!
return !flagToUse;
}
```
### decodeMatrixVariables
- 编码修改方法
```java
public MultiValueMap<String, String> decodeMatrixVariables(
HttpServletRequest request, MultiValueMap<String, String> vars) {
// 判断是否需要重写编码
if (this.urlDecode) {
return vars;
}
else {
// 需要重写编码的情况
MultiValueMap<String, String> decodedVars = new LinkedMultiValueMap<>(vars.size());
// 循环, 将 value 调用decodeInternal写到结果map返回
vars.forEach((key, values) -> {
for (String value : values) {
decodedVars.add(key, decodeInternal(request, value));
}
});
return decodedVars;
}
}
```
- 与这个方法对应的还有`decodePathVariables`
### decodePathVariables
```java
public Map<String, String> decodePathVariables(HttpServletRequest request, Map<String, String> vars) {
// 判断是否需要重写编码
if (this.urlDecode) {
return vars;
}
else {
Map<String, String> decodedVars = new LinkedHashMap<>(vars.size());
// 虚幻 decoding
vars.forEach((key, value) -> decodedVars.put(key, decodeInternal(request, value)));
return decodedVars;
}
}
```
- 回到`org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#getHandlerInternal`
```JAVA
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
```
- 设置属性上锁开锁就不具体展开了.
## lookupHandlerMethod
- `org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#lookupHandlerMethod` 方法
- 第一部分
```java
@Nullable
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
List<Match> matches = new ArrayList<>();
// 从 MultiValueMap 获取
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
// 如果不为空
if (directPathMatches != null) {
// 添加匹配映射
addMatchingMappings(directPathMatches, matches, request);
}
if (matches.isEmpty()) {
// No choice but to go through all mappings...
// 添加匹配映射
addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}
//...
}
```
- 创建一个匹配 list,将匹配结果放入
```
List<Match> matches = new ArrayList<>();
```
- 从 map 中获取数据
```
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
```
```JAVA
@Nullable
public List<T> getMappingsByUrl(String urlPath) {
return this.urlLookup.get(urlPath);
}
```
urlLookup 是`MultiValueMap`接口.
key:url value:mapping
- addMatchingMappings 方法
```java
if (directPathMatches != null) {
// 添加匹配映射
addMatchingMappings(directPathMatches, matches, request);
}
if (matches.isEmpty()) {
// No choice but to go through all mappings...
// 添加匹配映射
addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}
```
```java
private void addMatchingMappings(Collection<T> mappings, List<Match> matches, HttpServletRequest request) {
for (T mapping : mappings) {
// 抽象方法
// 通过抽象方法获取 match 结果
T match = getMatchingMapping(mapping, request);
// 是否为空
if (match != null) {
// 从 mappingLookup 获取结果并且插入到matches中
matches.add(new Match(match, this.mappingRegistry.getMappings().get(mapping)));
}
}
}
```
- `getMatchingMapping` 方法是一个抽象方法
```java
protected abstract T getMatchingMapping(T mapping, HttpServletRequest request);
```
- `org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping#getMatchingMapping`
```java
@Override
protected RequestMappingInfo getMatchingMapping(RequestMappingInfo info, HttpServletRequest request) {
return info.getMatchingCondition(request);
}
```
- 第二部分
```java
if (!matches.isEmpty()) {
// 比较对象
Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
// 排序
matches.sort(comparator);
// 获取第一个 match 对象
Match bestMatch = matches.get(0);
if (matches.size() > 1) {
if (logger.isTraceEnabled()) {
logger.trace(matches.size() + " matching mappings: " + matches);
}
if (CorsUtils.isPreFlightRequest(request)) {
return PREFLIGHT_AMBIGUOUS_MATCH;
}
Match secondBestMatch = matches.get(1);
if (comparator.compare(bestMatch, secondBestMatch) == 0) {
// 拿出 handlerMethod 进行比较
Method m1 = bestMatch.handlerMethod.getMethod();
Method m2 = secondBestMatch.handlerMethod.getMethod();
String uri = request.getRequestURI();
throw new IllegalStateException(
"Ambiguous handler methods mapped for '" + uri + "': {" + m1 + ", " + m2 + "}");
}
}
request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.handlerMethod);
handleMatch(bestMatch.mapping, lookupPath, request);
return bestMatch.handlerMethod;
}
else {
return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
}
```
- 一行行开始分析
```java
Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
```
- 抽象方法`getMappingComparator`
```java
protected abstract Comparator<T> getMappingComparator(HttpServletRequest request);
```
- 实现方法
```java
@Override
protected Comparator<RequestMappingInfo> getMappingComparator(final HttpServletRequest request) {
return (info1, info2) -> info1.compareTo(info2, request);
}
```
内部定义了 compareTo 方法
- 执行完成比较方法后创建对象`MatchComparator`
- 对象创建后进行排序,排序后取出第一个元素作为后续操作的基准对象
```java
// 排序
matches.sort(comparator);
// 获取第一个 match 对象
Match bestMatch = matches.get(0);
```
```java
if (matches.size() > 1) {
if (logger.isTraceEnabled()) {
logger.trace(matches.size() + " matching mappings: " + matches);
}
// 是否跨域请求
if (CorsUtils.isPreFlightRequest(request)) {
return PREFLIGHT_AMBIGUOUS_MATCH;
}
// 取出第二个元素.
Match secondBestMatch = matches.get(1);
// 如果比较结果相同
if (comparator.compare(bestMatch, secondBestMatch) == 0) {
// 第二个元素和第一个元素的比较过程
// 拿出 handlerMethod 进行比较
Method m1 = bestMatch.handlerMethod.getMethod();
Method m2 = secondBestMatch.handlerMethod.getMethod();
String uri = request.getRequestURI();
throw new IllegalStateException(
"Ambiguous handler methods mapped for '" + uri + "': {" + m1 + ", " + m2 + "}");
}
}
```
- 取出第一个元素和第二个元素进行比较. 如果两个 match 相同, 出现异常
最后两个方法
```java
// 设置属性
request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.handlerMethod);
// 处理匹配的结果
handleMatch(bestMatch.mapping, lookupPath, request);
return bestMatch.handlerMethod;
}
else {
// 处理没有匹配的结果
return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
}
```
- `handleMatch`
```java
protected void handleMatch(T mapping, String lookupPath, HttpServletRequest request) {
request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, lookupPath);
}
```
设置一次属性
这个方法子类会继续实现
- `org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping#handleMatch`
```java
@Override
protected void handleMatch(RequestMappingInfo info, String lookupPath, HttpServletRequest request) {
super.handleMatch(info, lookupPath, request);
String bestPattern;
Map<String, String> uriVariables;
// 匹配器
Set<String> patterns = info.getPatternsCondition().getPatterns();
// 如果空设置基本数据
if (patterns.isEmpty()) {
bestPattern = lookupPath;
uriVariables = Collections.emptyMap();
}
else {
// 取出一个匹配器
bestPattern = patterns.iterator().next();
// 地址匹配器比较 路由地址和匹配器比较
uriVariables = getPathMatcher().extractUriTemplateVariables(bestPattern, lookupPath);
}
request.setAttribute(BEST_MATCHING_PATTERN_ATTRIBUTE, bestPattern);
if (isMatrixVariableContentAvailable()) {
// 处理多层参数, 带有;分号的处理
Map<String, MultiValueMap<String, String>> matrixVars = extractMatrixVariables(request, uriVariables);
request.setAttribute(HandlerMapping.MATRIX_VARIABLES_ATTRIBUTE, matrixVars);
}
// 编码url参数
Map<String, String> decodedUriVariables = getUrlPathHelper().decodePathVariables(request, uriVariables);
request.setAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, decodedUriVariables);
if (!info.getProducesCondition().getProducibleMediaTypes().isEmpty()) {
// 获取 media type
Set<MediaType> mediaTypes = info.getProducesCondition().getProducibleMediaTypes();
request.setAttribute(PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE, mediaTypes);
}
}
```
- `handleNoMatch` 也是同类型操作
- `org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#handleNoMatch`
- `org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping#handleNoMatch`
```java
@Override
protected HandlerMethod handleNoMatch(
Set<RequestMappingInfo> infos, String lookupPath, HttpServletRequest request) throws ServletException {
// 创建对象 PartialMatchHelper
PartialMatchHelper helper = new PartialMatchHelper(infos, request);
if (helper.isEmpty()) {
return null;
}
// 函数是否匹配
if (helper.hasMethodsMismatch()) {
Set<String> methods = helper.getAllowedMethods();
// 请求方式比较
if (HttpMethod.OPTIONS.matches(request.getMethod())) {
// handler 转换
HttpOptionsHandler handler = new HttpOptionsHandler(methods);
// 构建 handler method
return new HandlerMethod(handler, HTTP_OPTIONS_HANDLE_METHOD);
}
throw new HttpRequestMethodNotSupportedException(request.getMethod(), methods);
}
if (helper.hasConsumesMismatch()) {
Set<MediaType> mediaTypes = helper.getConsumableMediaTypes();
MediaType contentType = null;
if (StringUtils.hasLength(request.getContentType())) {
try {
// 字符串转换成对象
contentType = MediaType.parseMediaType(request.getContentType());
}
catch (InvalidMediaTypeException ex) {
throw new HttpMediaTypeNotSupportedException(ex.getMessage());
}
}
throw new HttpMediaTypeNotSupportedException(contentType, new ArrayList<>(mediaTypes));
}
if (helper.hasProducesMismatch()) {
Set<MediaType> mediaTypes = helper.getProducibleMediaTypes();
throw new HttpMediaTypeNotAcceptableException(new ArrayList<>(mediaTypes));
}
if (helper.hasParamsMismatch()) {
List<String[]> conditions = helper.getParamConditions();
throw new UnsatisfiedServletRequestParameterException(conditions, request.getParameterMap());
}
return null;
}
```