tomcat共享多個web應用會話的實現方法
問題
今天有位朋友問了個問題，大致是：tomcat下兩個Java web，一個是商城，一個是直播，從商城登錄后，再跳轉到直播，發現處于非登錄狀態。
解決思路
- 將session抽出來成一個session服務，統一通過該服務操作session。
- tomcat內部用會話管理器獲取會話時遍歷所有context內的會話。
方案1
重寫獲取session方法即可。
方案2
找了源碼發現已經支持類似遍歷所有context內的會話的形式，首先獲取session時，如果cressContext屬性為true，則會在獲取不到時嘗試遍歷所有context是否存在該sessionid，如果存在則在本context根據sessionid創建自己的session對象。
public HttpSession getSession(boolean create) {
if (crossContext) {
// There cannot be a session if no context has been assigned yet
if (context == null)
return (null);
// Return the current session if it exists and is valid
if (session != null session.isValid()) {
return (session.getSession());
}
HttpSession other = super.getSession(false);
if (create (other == null)) {
// First create a session in the first context: the problem is
// that the top level request is the only one which can
// create the cookie safely
other = super.getSession(true);
}
if (other != null) {
Session localSession = null;
try {
localSession =
context.getManager().findSession(other.getId());
if (localSession != null !localSession.isValid()) {
localSession = null;
}
} catch (IOException e) {
// Ignore
}
if (localSession == null create) {
localSession =
context.getManager().createSession(other.getId());
}
if (localSession != null) {
localSession.access();
session = localSession;
return session.getSession();
}
}
return null;
} else {
return super.getSession(create);
}
}
context（web應用）獲取跨應用session時通過類似下面操作獲取：
request.getSession().getServletContext().getContext("/app2").getAttribute("att2");
這是因為request會根據cookies的sessionid獲取到session對象，這時不會報找不到，因為前面已經根據其他sessionid創建了一個session對象，然后getContext操作會獲取對應url的context，接著進行會話操作。
public ServletContext getContext(String uri) {
// Validate the format of the specified argument
if (uri == null || !uri.startsWith("/")) {
return null;
}
Context child = null;
try {
// Look for an exact match
Container host = context.getParent();
child = (Context) host.findChild(uri);
// Non-running contexts should be ignored.
if (child != null !child.getState().isAvailable()) {
child = null;
}
// Remove any version information and use the mapper
if (child == null) {
int i = uri.indexOf("##");
if (i > -1) {
uri = uri.substring(0, i);
}
// Note: This could be more efficient with a dedicated Mapper
// method but such an implementation would require some
// refactoring of the Mapper to avoid copy/paste of
// existing code.
MessageBytes hostMB = MessageBytes.newInstance();
hostMB.setString(host.getName());
MessageBytes pathMB = MessageBytes.newInstance();
pathMB.setString(uri);
MappingData mappingData = new MappingData();
((Engine) host.getParent()).getService().findConnectors()[0].getMapper().map(
hostMB, pathMB, null, mappingData);
child = (Context) mappingData.context;
}
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
return null;
}
if (child == null) {
return null;
}
if (context.getCrossContext()) {
// If crossContext is enabled, can always return the context
return child.getServletContext();
} else if (child == context) {
// Can still return the current context
return context.getServletContext();
} else {
// Nothing to return
return null;
}
}
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