Develop Reference

(ActiveJpa) Issue with the ActiveJpa 'like' filter

The like condition operator in ActiveJpa performs unexpectedly when the comparison string consists of Special Characters.
This is for a REST API built using the Java 8 Dropwizard framework.
str = "%"+str+"%"
filter.addCondition("column", Condition.Operator.like, str)
Initial thoughts were that ActiveJpa filters out all the special characters. But, the following change also does not work.
filter.addCondition("column", Condition.Operator.like, str.replace("+",""))
When the following string value is passed,
str = "+1212"
It returns null even if, corresponding results exist.

How to receive string array from servlet request in java [duplicate]

How can i send an Array with a HTTP Get request?
I'm Using GWT client to send the request.

I know this post is really old, but I have to reply because although BalusC's answer is marked as correct, it's not completely correct.
You have to write the query adding "[]" to foo like this:
foo[]=val1&foo[]=val2&foo[]=val3

That depends on what the target server accepts. There is no definitive standard for this. See also a.o. Wikipedia: Query string:
While there is no definitive standard, most web frameworks allow multiple values to be associated with a single field (e.g. field1=value1&field1=value2&field2=value3).[4][5]
Generally, when the target server uses a strong typed programming language like Java (Servlet), then you can just send them as multiple parameters with the same name. The API usually offers a dedicated method to obtain multiple parameter values as an array.
foo=value1&foo=value2&foo=value3
String[] foo = request.getParameterValues("foo"); // [value1, value2, value3]
The request.getParameter("foo") will also work on it, but it'll return only the first value.
String foo = request.getParameter("foo"); // value1
And, when the target server uses a weak typed language like PHP or RoR, then you need to suffix the parameter name with braces [] in order to trigger the language to return an array of values instead of a single value.
foo[]=value1&foo[]=value2&foo[]=value3
$foo = $_GET["foo"]; // [value1, value2, value3]
echo is_array($foo); // true
In case you still use foo=value1&foo=value2&foo=value3, then it'll return only the first value.
$foo = $_GET["foo"]; // value1
echo is_array($foo); // false
Do note that when you send foo[]=value1&foo[]=value2&foo[]=value3 to a Java Servlet, then you can still obtain them, but you'd need to use the exact parameter name including the braces.
String[] foo = request.getParameterValues("foo[]"); // [value1, value2, value3]

Java - generating conditions from string

I'm trying to generate some conditions using string i get as input.
For example, i get as in put the string "length = 15" and i want to create from that the condition:
length == 15.
To be more specific, i have an int in my program called length and it is set to a specific value.
i want to get from the user a conditon as input ("length < 15" or "length = 15"....) and create an if statement that generates the condition and test it.
What is the best way of doing that?
Thanks a lot
Ben

Unless you're talking about code-generation (i.e. generating Java-code by input strings) you can't generate an if-statement based on a string.
You'll have to write a parser for your condition-language, and interpret the resulting parse trees.
In the end it would look something like this:
Condition cond = ConditionParser.parse("length = 15");
if (cond.eval()) {
// condition is true
}

Use a string tokenizer. The default method to distinguish between tokens (or the smallest parts of the input string) is white space, which is to your benefit.
check out javadocs for details:
http://docs.oracle.com/javase/1.3/docs/api/java/util/StringTokenizer.html

Depending on what restrictions you can place on your input format, you could consider using Rhino to embed Javascript. Your 'conditions' then just have to be valid JavaScript code. Something like this (disclaimer: haven't compiled it):
import javax.script.*;
public bool evalCondition (Object context, String javascript) {
ScriptEngine engine = new ScriptEngineManager().getEngineByName("javascript");
Object result = engine.eval(javascript);
Boolean condTrue = (Boolean)result;
return condTrue;
}
See the Embedding Rhino Tutorial for more details.

Rhino: How to return a string from Java to Javascript?

How do I use Rhino return a string from Java to Javascript, all I get is org.mozilla.javascript.JavaNativeObject when I use
var jsString = new java.lang.String("test");
inside my js file.
Is this the right way to do it?
var jsString = String(new java.lang.String("test"));
The goal is to have a Java method to return the String object instead of creating it on the fly like above.

In general, you would call Context.javaToJS which converts a Java object to its closest representation in Javascript. However, for String objects, that function returns the string itself without needing to wrap it. So if you're always returning a string, you don't need to do anything special.

Although in most cases the returned Java String type can be used just like the JS String type within the JS code, it does not have the same methods!
In particular I found it cannot be used in a JS object passed to 'stringify()' as it does not have the toJSON() method.
The only solution I found is to explicitly do the addition of "" in the JS, to convert the Java String to a JS String. I found no way to code the java method to return a good JS string directly... (as Context.javaToJS() doesn't convert a Java String)
Eg:
var jstr = MyJavaObj.methodReturningAString();
JSON.stringify({ "toto":jstr}); // Fails
JSON.stringify({ "toto": ""+jstr}); // OK

Turn off the wrapping of Primitives and then the value returned in your expression will be a JS string:
Context cx = Context.enter();
cx.getWrapFactory().setJavaPrimitiveWrap(false);

For me this is a Rhino bug. The s+"" trick inside JavaScript works, but here's a quick patch to fix it Java-side - after this line in NativeJavaMethod.call()
Object retval = meth.invoke(javaObject, args);
add this check to convert it to a native JavaScript string (ie typeof returns "string" not "object")
if (retval instanceof String) {
return NativeJavaObject.coerceTypeImpl(String.class, retval);
}
This is important otherwise s.replace() calls the Java version so is wrong for eg "h e l l o".replace(" ", "")
https://github.com/mozilla/rhino/issues/638

Java -> Apache Commons StringEscapeUtils -> escapeJavaScript

For a very simple ajax name lookup, I'm sending an id from the client webpage to the server (Tomcat 5.5, Java 5), looking it up in a database and returning a string, which is assigned to a javascript variable back in the client (and then displayed).
The javascript code that receives the value is pretty standard:
//client code - javascript
xmlHttp.onreadystatechange=function() {
if (xmlHttp.readyState==4) {
var result = xmlHttp.responseText;
alert(result);
...
}
...
}
To return the string, I originally had this in the server:
//server code - java
myString = "...";
out.write(myString.getBytes("UTF-8"));
Which worked perfectly, if unsafe. Later, I replaced it with:
import org.apache.commons.lang.StringEscapeUtils;
...
myString = "...";
out.write(StringEscapeUtils.escapeJavaScript(myString).getBytes("UTF-8"));
But while safer, the resulting string can't be properly displayed if it contains special chars like "ñ".
For instance, using:
escapeJavaScript("años").getBytes("UTF-8");
sends:
an\u00F1os
to the client.
The question: is there a simple way to parse the resulting string in Javascript or is there an alternate escape function I can use in java that would prevent this issue?

The following works in every browser I've tried:
javascript:alert("a\u00F1os");
Perhaps your string is being escaped twice by mistake.

Actually, now that I read it over, I think I actually don't need to escape the string I'm sending back at all... That is, StringEscapeUtils.escapeJavaScript would be useful if the resulting value was printed in the page, like:
//javascript code with inline struts
var myJavasriptString = "<%=myJavaString%>";
Or am I missing something and there would still be a valid reason to do the escape in the original case? (when it is returned as a series of bytes back to an ajax onreadystatechange handler and assigned to a js variable)