Converting a Java ArrayList of strings to a JavaScript array

Question

In my Java code, I have an ArrayList of Strings. I'd like to put this data in a JavaScript variable on a JSP page I'm working on. My first thought was to include it directly, e.g.:

var myArray = <%= arrayList %>;

Unfortunately, when executed, myArray is a string in the format [a,b,c], not an actual JavaScript array. How do I get some data from a Java ArrayList to a JavaScript array?

Alvin

please add more code with an example data – Borosilicate

Answer 1

When you use <%=arraylist%> it calls the toString() on list and prints [a,b,c]

And No,you cannot direclty convert From Java arrayList to javascript array ,Convert the Java ArrayList to JSON String, and use JSON.parse() to get Javascript object.

Have a look at Json objet and Json in java

Pyemia

Thanks buddy. I have the json string like [a,b,c]. When i use Json.parse(aa); It shows the error. Uncaught reference error.a is not defined. So it must be like ["a","b","c"]. So how to convert like this? – Alvin

Dude,you have to add json library to your class path and convert your arraylist on serverside to json string and send it to client.Then JSON.parse() works :) – Pyemia

The second link in the answer is not available anymore. – Kylstra

Answer 2

Withoug a library:

Java:

public static String toJavascriptArray(String[] arr){
    StringBuffer sb = new StringBuffer();
    sb.append("[");
    for(int i=0; i<arr.length; i++){
        sb.append("\"").append(arr[i]).append("\"");
        if(i+1 < arr.length){
            sb.append(",");
        }
    }
    sb.append("]");
    return sb.toString();
}

JSP:

var myArray = <%= toJavascriptArray(arrayList) %>;

Rambo

Technique is good, but still you need to parse it to JSON, while assigning to javascript variable. – Credulous

Answer 3

Do the following in your JSP page

<% List<String> strList = new ArrayList<String>();
strList.add("one");
strList.add("two");
strList.add("three"); %>

var jsArray = [<% for (int i = 0; i < strList.size(); i++) { %>"<%= strList.get(i) %>"<%= i + 1 < strList.size() ? ",":"" %><% } %>];

The output will be

var jsArray = ["one","two","three"];

If your List was empty it will output

var jsArray = [];

Dagenham

Answer 4

The JavaScript split() method returns an array, so it's a simple way to convert a Java ArrayList into a JavaScript array.

function toJavascript(){
    var array="<%=javaArrayList%>";
    array=array.replace("[", "");
    array=array.replace("]", "");
    return javaArray.split(",");
}

Oribelle

Answer 5

try this way:

var myArray = <%=net.sf.json.JSONSerializer.toJSON(arrayList) %>;

Whiteley

Answer 6

Simple

 var jsArray = JSON.parse(yourJavaListObject)

Scampi