java动态开发groovy,如何从Java中的字符串动态创建Groovy闭包

I would like to know how to create a Closure object at run-time from within a Java application, where the content of the Closure is not known ahead of time. I have found a solution but I doubt that it is optimal.

Background: I have written some Groovy code that parses a Domain Specific Language. The parsing code is statically compiled and included in a Java application. In the parser implementation I have classes acting as delegates for specific sections of the DSL. These classes are invoked using the following pattern:

class DslDelegate {

private Configuration configuration

def section(@DelegatesTo(SectionDelegate) Closure cl) {

cl.delegate = new SectionDelegate(configuration)

cl.resolveStrategy = Closure.DELEGATE_FIRST

cl()

}

}

I wish to call such a method directly from Java code. I am able to create a new DslDelegate object and then invoke the section() method. However I need to create and pass an argument that is an instance of Closure. I want the content to be initialised from a String object.

My Solution: The following Java code (utility) is working but I am asking for improvements. Surely this can be done in a cleaner or more efficient manner?

/**

* Build a Groovy Closure dynamically

*

* @param strings

* an array of strings for the text of the Closure

* @return a Groovy Closure comprising the specified text from {@code strings}

* @throws IOException

*/

public Closure> buildClosure(String... strings) throws IOException {

Closure> closure = null;

// Create a method returning a closure

StringBuilder sb = new StringBuilder("def closure() { { script -> ");

sb.append(String.join("n", strings));

sb.append(" } }");

// Create an anonymous class for the method

GroovyClassLoader loader = new GroovyClassLoader();

Class> groovyClass = loader.parseClass(sb.toString());

try {

// Create an instance of the class

GroovyObject groovyObject = (GroovyObject) groovyClass.newInstance();

// Invoke the object's method and thus obtain the closure

closure = (Closure>) groovyObject.invokeMethod("closure", null);

} catch (InstantiationException | IllegalAccessException e) {

throw new RuntimeException(e);

} finally {

loader.close();

}

return closure;

}

解决方案

You can use GroovyShell to create a Closure from strings:

public Closure> buildClosure(String... strings) {

String scriptText = "{ script -> " + String.join("n", strings) + " }";

return (Closure>) new GroovyShell().evaluate(scriptText);

}