Compiling JavaScript using Java SE 5

This blogs talks about how to compile JavaScript from Java

Requirement:

1) Java SE 5
2) jsr223-1.0.jar (http://jcp.org/en/jsr/detail?id=223)
3) js-14.jar (http://www.mozilla.org/rhino/)
4) js.jar (http://www.mozilla.org/rhino/)

Note if you are using Java SE 6 then none of the above jar are needed as it is part of jdk.

Writing a test class:

import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

/**
*
* @author milind
*/
public class JavaScriptCompileTest {

/**
* @param args the command line arguments
*/
public static void main(String[] args) {

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByExtension("js");
if (engine instanceof Compilable) {
Compilable compEngine = (Compilable) engine;
try {
CompiledScript script = compEngine.compile("function count(){ var count; function myName() { document};");
} catch (ScriptException e) {
System.out.println("Message : " + e.getCause().getMessage() );
}
} else {
System.err.println("Engine can't compile code the code Scripting Engine Missing");
}
}
}

It will print following on console:
Message : missing } after function body along with stack trace.

Attaching New Object Dynamically To Spring Context

Many times it is required to attach new custom object dynamically to a Spring Context.

Here are the steps to do that:

1) First Step is to create a new custom object which will be dynamically attached to the Spring Context.


package com.milind.BeanAttach;

/**
*
* @author milind
*/
public class TestBean {

private String name;

public TestBean() {
}

private int age;

public TestBean(String name, int age) {
this.name = name;
this.age = age;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

@Override
public String toString() {
return "Name: "+this.name+ " Age: "+ this.age;
}

}

2) Now we need to create our own custom BeanFactory by implementing the FactoryBean interface.
package com.milind.BeanAttach;

import java.util.HashMap;
import java.util.Map;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.FactoryBean;

/**
*
* @author milind
*/
public class AttachBean implements BeanNameAware, FactoryBean {

public static Map beanMap = new HashMap();

public static Map getBeanMap() {
return beanMap;
}

public static void setBeanMap(Map beanMap) {
AttachBean.beanMap = beanMap;
}

private String beanName;

public void setBeanName(String arg0) {

System.out.println("In Set Bean Name .....");
this.beanName= arg0;
}

public Object getObject() throws Exception {
System.out.println("In get Object .....");
return beanMap.get(this.beanName);
}

public Class getObjectType() {
return beanMap.get(this.beanName).getClass();
}

public boolean isSingleton() {
return false;
}
}

3) Creating the applicationContext.xml

Here is the how the applicationContext.xml will look like:


4) Creating the Client to test

package com.milind.BeanAttach;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
*
* @author milind
*/
public class BeanTest {

public static void main(String[] args) {

TestBean obj = new TestBean("Tanmay", 4);
AttachBean.beanMap.put("attach_object", obj);
ApplicationContext ctx = new ClassPathXmlApplicationContext("com/milind/BeanAttach/applicationContext.xml");
TestBean gotObj = (TestBean)ctx.getBean("attach_object");
print(gotObj.toString());

print("Assigning new Object .........................................");
AttachBean.beanMap.put("attach_object", new TestBean("Guest", 99));
gotObj = (TestBean)ctx.getBean("attach_object");
print(gotObj.toString());
}

private static void print(String s) {
System.out.println(s);
}

}


Now you can attach object of any type to the same bean id. Only you had to cast it appropriately when you get the object from context.