之前说到对请求行和请求头进行解析，获取到请求信息，现在我们有了请求信息，就要根据请求url映射到servlet进行处理，接下来开始看这个过程。tomcat处理请求的线程中CoyoteAdapter.java的service中,通过postParseRequest(req, request, res, response);方法根据请求url映射相关容器，映射容器的过程是在connector.getService().getMapper().map(serverName, decodedURI, version, request.getMappingData());中实现的。
- 定位Context
通过uri字符串和context的name字符串匹配，uri必须以context的name开头，且下一个字符为 ‘/’，则认为找到了context。
private void internalMap(CharChunk host, CharChunk uri, String version, MappingData mappingData)
throws IOException {
......
MappedHost[] hosts = this.hosts;
//忽略大小写匹配路径，找到 MappedHost
MappedHost mappedHost = exactFindIgnoreCase(hosts, host);
if (mappedHost == null) {
// 没有找到的话，从第二个 "." 开始向后查找
int firstDot = host.indexOf('.');
if (firstDot > -1) {
int offset = host.getOffset();
try {
host.setOffset(firstDot + offset);
mappedHost = exactFindIgnoreCase(hosts, host);
} finally {
// Make absolutely sure this gets reset
host.setOffset(offset);
}
}
if (mappedHost == null) {
mappedHost = defaultHost;
if (mappedHost == null) {
return;
}
}
}
mappingData.host = mappedHost.object;
if (uri.isNull()) {
// Can't map context or wrapper without a uri
return;
}
uri.setLimit(-1);
// 映射Context
ContextList contextList = mappedHost.contextList;
MappedContext[] contexts = contextList.contexts;
//到MappedContext[]中根据uri遍历，找到uri包含Context Name的Context
int pos = find(contexts, uri);
if (pos == -1) {
return;
}
int lastSlash = -1;
int uriEnd = uri.getEnd();
int length = -1;
boolean found = false;
MappedContext context = null;
while (pos >= 0) {
context = contexts[pos];
if (uri.startsWith(context.name)) {
length = context.name.length();
//uri长度和context的name长度相等，说明找到了对应的context，但是没有servlet
if (uri.getLength() == length) {
found = true;
break;
//uri中从context的name的长度开始的字符串是否为/，是则找到
//例如 /MyXmlApp/myservlet 中找到一个 name为 /MyXmlApp 的context，并且name的下个字符串是 /
//意思是 uri必须包含context的name，并且下一个字符为 "/"
} else if (uri.startsWithIgnoreCase("/", length)) {
found = true;
break;
}
}
if (lastSlash == -1) {
lastSlash = nthSlash(uri, contextList.nesting + 1);
} else {
lastSlash = lastSlash(uri);
}
uri.setEnd(lastSlash);
pos = find(contexts, uri);
}
uri.setEnd(uriEnd);
if (!found) {
if (contexts[0].name.equals("")) {
context = contexts[0];
} else {
context = null;
}
}
if (context == null) {
return;
}
mappingData.contextPath.setString(context.name);
ContextVersion contextVersion = null;
ContextVersion[] contextVersions = context.versions;
final int versionCount = contextVersions.length;
if (versionCount > 1) {
Context[] contextObjects = new Context[contextVersions.length];
for (int i = 0; i < contextObjects.length; i++) {
contextObjects[i] = contextVersions[i].object;
}
mappingData.contexts = contextObjects;
if (version != null) {
contextVersion = exactFind(contextVersions, version);
}
}
if (contextVersion == null) {
// Return the latest version
// The versions array is known to contain at least one element
contextVersion = contextVersions[versionCount - 1];
}
mappingData.context = contextVersion.object;
mappingData.contextSlashCount = contextVersion.slashCount;
// 映射servlet，servlet是由Wrapper封装的
if (!contextVersion.isPaused()) {
internalMapWrapper(contextVersion, uri, mappingData);
}
}
- 定位servlet
定位servlet是一个很长的过程，由于平时我们大多都是精准路径匹配，所以我就看了前面一点，后面还有模糊匹配等方式没有深入去看了。过程其实很简单，在uri中把context对应的路径字符串去掉，后面的字符串就是servlet映射的请求url路径，根据此路径调用internalMapExactWrapper方法，到MappedWrapper[] wrappers数组中，匹配对应的MappedWrapper即可。
private void internalMapWrapper(ContextVersion contextVersion, CharChunk path, MappingData mappingData)
throws IOException {
int pathOffset = path.getOffset();
int pathEnd = path.getEnd();
boolean noServletPath = false;
int length = contextVersion.path.length();
//如果只有context路径，则无对应的servlet
if (length == (pathEnd - pathOffset)) {
noServletPath = true;
}
//servlet路径在context路径后面
int servletPath = pathOffset + length;
//截取context路径后面的字符串
path.setOffset(servletPath);
// Rule 1 -- Exact Match
MappedWrapper[] exactWrappers = contextVersion.exactWrappers;
internalMapExactWrapper(exactWrappers, path, mappingData);
// Rule 2 -- Prefix Match
boolean checkJspWelcomeFiles = false;
MappedWrapper[] wildcardWrappers = contextVersion.wildcardWrappers;
if (mappingData.wrapper == null) {
internalMapWildcardWrapper(wildcardWrappers, contextVersion.nesting, path, mappingData);
if (mappingData.wrapper != null && mappingData.jspWildCard) {
char[] buf = path.getBuffer();
if (buf[pathEnd - 1] == '/') {
/*
* Path ending in '/' was mapped to JSP servlet based on wildcard match (e.g., as specified in
* url-pattern of a jsp-property-group. Force the context's welcome files, which are interpreted as
* JSP files (since they match the url-pattern), to be considered. See Bugzilla 27664.
*/
mappingData.wrapper = null;
checkJspWelcomeFiles = true;
} else {
// See Bugzilla 27704
mappingData.wrapperPath.setChars(buf, path.getStart(), path.getLength());
mappingData.pathInfo.recycle();
}
}
}
if (mappingData.wrapper == null && noServletPath &&
contextVersion.object.getMapperContextRootRedirectEnabled()) {
// The path is empty, redirect to "/"
path.append('/');
pathEnd = path.getEnd();
mappingData.redirectPath.setChars(path.getBuffer(), pathOffset, pathEnd - pathOffset);
path.setEnd(pathEnd - 1);
return;
}
// Rule 3 -- Extension Match
MappedWrapper[] extensionWrappers = contextVersion.extensionWrappers;
if (mappingData.wrapper == null && !checkJspWelcomeFiles) {
internalMapExtensionWrapper(extensionWrappers, path, mappingData, true);
}
// Rule 4 -- Welcome resources processing for servlets
if (mappingData.wrapper == null) {
boolean checkWelcomeFiles = checkJspWelcomeFiles;
if (!checkWelcomeFiles) {
char[] buf = path.getBuffer();
checkWelcomeFiles = (buf[pathEnd - 1] == '/');
}
if (checkWelcomeFiles) {
for (int i = 0; (i < contextVersion.welcomeResources.length) && (mappingData.wrapper == null); i++) {
path.setOffset(pathOffset);
path.setEnd(pathEnd);
path.append(contextVersion.welcomeResources[i], 0, contextVersion.welcomeResources[i].length());
path.setOffset(servletPath);
// Rule 4a -- Welcome resources processing for exact macth
internalMapExactWrapper(exactWrappers, path, mappingData);
// Rule 4b -- Welcome resources processing for prefix match
if (mappingData.wrapper == null) {
internalMapWildcardWrapper(wildcardWrappers, contextVersion.nesting, path, mappingData);
}
// Rule 4c -- Welcome resources processing
// for physical folder
if (mappingData.wrapper == null && contextVersion.resources != null) {
String pathStr = path.toString();
WebResource file = contextVersion.resources.getResource(pathStr);
if (file != null && file.isFile()) {
internalMapExtensionWrapper(extensionWrappers, path, mappingData, true);
if (mappingData.wrapper == null && contextVersion.defaultWrapper != null) {
mappingData.wrapper = contextVersion.defaultWrapper.object;
mappingData.requestPath.setChars(path.getBuffer(), path.getStart(), path.getLength());
mappingData.wrapperPath.setChars(path.getBuffer(), path.getStart(), path.getLength());
mappingData.requestPath.setString(pathStr);
mappingData.wrapperPath.setString(pathStr);
}
}
}
}
path.setOffset(servletPath);
path.setEnd(pathEnd);
}
}
/*
* welcome file processing - take 2 Now that we have looked for welcome files with a physical backing, now look
* for an extension mapping listed but may not have a physical backing to it. This is for the case of index.jsf,
* index.do, etc. A watered down version of rule 4
*/
if (mappingData.wrapper == null) {
boolean checkWelcomeFiles = checkJspWelcomeFiles;
if (!checkWelcomeFiles) {
char[] buf = path.getBuffer();
checkWelcomeFiles = (buf[pathEnd - 1] == '/');
}
if (checkWelcomeFiles) {
for (int i = 0; (i < contextVersion.welcomeResources.length) && (mappingData.wrapper == null); i++) {
path.setOffset(pathOffset);
path.setEnd(pathEnd);
path.append(contextVersion.welcomeResources[i], 0, contextVersion.welcomeResources[i].length());
path.setOffset(servletPath);
internalMapExtensionWrapper(extensionWrappers, path, mappingData, false);
}
path.setOffset(servletPath);
path.setEnd(pathEnd);
}
}
// Rule 7 -- Default servlet
if (mappingData.wrapper == null && !checkJspWelcomeFiles) {
if (contextVersion.defaultWrapper != null) {
mappingData.wrapper = contextVersion.defaultWrapper.object;
mappingData.requestPath.setChars(path.getBuffer(), path.getStart(), path.getLength());
mappingData.wrapperPath.setChars(path.getBuffer(), path.getStart(), path.getLength());
mappingData.matchType = MappingMatch.DEFAULT;
}
// Redirection to a folder
char[] buf = path.getBuffer();
if (contextVersion.resources != null && buf[pathEnd - 1] != '/') {
String pathStr = path.toString();
// Note: Check redirect first to save unnecessary getResource()
// call. See BZ 62968.
if (contextVersion.object.getMapperDirectoryRedirectEnabled()) {
WebResource file;
// Handle context root
if (pathStr.length() == 0) {
file = contextVersion.resources.getResource("/");
} else {
file = contextVersion.resources.getResource(pathStr);
}
if (file != null && file.isDirectory()) {
// Note: this mutates the path: do not do any processing
// after this (since we set the redirectPath, there
// shouldn't be any)
path.setOffset(pathOffset);
path.append('/');
mappingData.redirectPath.setChars(path.getBuffer(), path.getStart(), path.getLength());
} else {
mappingData.requestPath.setString(pathStr);
mappingData.wrapperPath.setString(pathStr);
}
} else {
mappingData.requestPath.setString(pathStr);
mappingData.wrapperPath.setString(pathStr);
}
}
}
path.setOffset(pathOffset);
path.setEnd(pathEnd);
}
其实这样看，根据请求url映射servlet相关容器的过程并不复杂，本质就是字符串处理的过程。