JavaScriptTemplate looks for each
* <server language="javascript"> (or
* <javascript>)
* tag in an HTML page and treats the following data up to the next
* </server> (or </javascript>)
* tag as a JavaScript script to evaluate.
*
* The reason that JavaScript scripts are included in an HTML page is usually
* to generate dynamic, server-side content. After running this template,
* everything between and including the <server> and
* </server> (or <javascript> and
* </javascript> tags is replaced by all output written
* to the JavaScript standard output stream (if any).
*
* All JavaScript fragments within a given page are evaluated in the same JavaScript
* interpreter. The JavaScript interpreter actually lives for the entire duration
* of this Template object, so the user can implement
* persistence across requests.
*
* The following configuration parameters are used to initialize this * template.
prefix and
* server are set before this file is evaluated, and
* are references to the parameters passed to a handler
* init method.
* <server> and
* </server> tags with comments, so the user
* can keep track of where the dynamically generated content is coming
* from by examining the comments in the resultant HTML document.
* By default, the <server> and
* </server> are completely eliminated from the
* HTML document rather than changed into comments.
* * Before evaluating each HTML document, this class sets variables * in the JavaScript interpreter, which can be used to interact back with Java to * do things like set the response headers:
eval is present as an attribute, all
* constructs of the form ${...} are substituted before processing the
* script.
* * Here's a simple example of a JavaScript template: *
* <html>
* <head>
* <title>JavaScript Example</title>
* </head>
* <body>
* <javascript>
* var s = "request=" + request;
* s += "<br>request.serverUrl is " + request.serverUrl();
* s += "<br>server hostName is " + server.hostName;
* s += "<br>prefix is " + prefix;
* s += "<br> <table>";
*
* // This is an example of using Java in JavaScript with LiveConnect
* var e = request.props.propertyNames();
* while (e.hasMoreElements()) {
* var prop = e.nextElement();
* s += "<tr><td>" + prop + "</td>";
* s += "<td>" + request.props.getProperty(prop) + "</td></tr>";
* }
*
* s += "</table>";
*
* // The last value computed or expressed is returned
* s;
*
* </javascript>
* </body>
* </html>
* JavaScriptTemplate is asked to process.
*
* The first time this method is called, the initialization script is
* sourced into the interpreter, based on the configuration properties
* in the Request
*
* @param hr
* The request and associated HTML document that will be
* processed.
*
* @return true.
*/
public boolean
init(RewriteContext hr) {
hr.addClosingTag("javascript");
return super.init(hr);
}
private boolean
setup(RewriteContext hr) {
Properties props = hr.request.props;
scope = cx.initStandardObjects(null);
String script = props.getProperty(hr.prefix + SCRIPT);
try {
scope.put("prefix", scope, hr.prefix);
scope.put("server", scope, Context.toObject(hr.server, scope));
if (script != null) {
String body = ResourceHandler.getResourceString(props,
hr.prefix, script);
System.err.println("startup: " + body);
cx.evaluateString(scope, body, script, 1, null);
}
} catch (IOException e) {
hr.request.log(Server.LOG_ERROR, "reading init script", script);
Context.exit();
return false;
} catch (JavaScriptException e) {
hr.request.log(Server.LOG_ERROR, "initializing JavaScript",
e.toString());
Context.exit();
return false;
}
return true;
}
/**
* Processes the <server> tag. Substitutes the
* result of evaluating the following JavaScript script into the resultant
* HTML document.
*
* Note: Currently, there is no mechanism for other language interpreters
* to share the same server tag.
*
* @param hr
* The request and associated HTML document that will be
* processed.
*/
public void
tag_server(RewriteContext hr) {
if ("javascript".equals(hr.get("language")) == false) {
return;
}
tag_javascript(hr);
}
/**
* Processes the <javascript> tag. Substitutes the
* result of evaluating the following JavaScript script into the resultant
* HTML document.
*
* @param hr
* The request and associated HTML document that will be
* processed.
*/
public void
tag_javascript(RewriteContext hr) {
Thread thread;
debug(hr);
boolean eval = hr.isTrue("eval");
boolean was = hr.accumulate(false);
hr.nextToken();
String script = hr.getBody();
if (eval) {
script = Format.subst(hr.request.props, script);
}
hr.request.log(Server.LOG_DIAGNOSTIC, hr.prefix, "Setting request");
if ((thread = Thread.currentThread()) != current) {
if (cx != null) {
Context.exit();
}
cx = Context.enter();
current = thread;
}
if (scope == null) {
if (!setup(hr)) {
hr.accumulate(was);
return;
}
}
scope.put("request", scope, Context.toObject(hr.request, scope));
hr.request.log(Server.LOG_DIAGNOSTIC, hr.prefix, script);
Object result = null;
try {
result = cx.evaluateString(scope, script, "template", 1, null);
} catch (JavaScriptException e) {
hr.append("\n\n");
hr.request.log(Server.LOG_DIAGNOSTIC, hr.prefix, e.toString());
}
hr.nextToken();
if (result != cx.getUndefinedValue()) {
hr.append(cx.toString(result));
}
hr.accumulate(was);
}
}