https://github.com/edefazio/varcode

Generate, compile and run .java source dynamically at runtime
https://github.com/edefazio/varcode

api code generator java-source metaprogramming runtime

Last synced: 3 months ago
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Generate, compile and run .java source dynamically at runtime

• Host: GitHub
• URL: https://github.com/edefazio/varcode
• Owner: edefazio
• Created: 2016-09-01T16:44:30.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2019-04-23T01:09:03.000Z (over 5 years ago)
• Last Synced: 2024-06-21T22:43:13.788Z (5 months ago)
• Topics: api, code, generator, java-source, metaprogramming, runtime
• Language: Java
• Homepage:
• Size: 2.05 MB
• Stars: 11
• Watchers: 3
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        


combines a **code generator** and **ad-hoc tools** to **compile, load, and run .java source code at runtime**.  

## generate / run / export .java code at runtime ##

```java

//1 generate a model

_class _model = _class.of( "package mymodel;", 

    "public class Model" )

    .imports( UUID.class )

    .method( "public String createId()",

        "return UUID.randomUUID().toString();" );

// 2) create instance        

Object dynamicModel = _model.instance();        

// 3) call a method on the dynamic instance

String id1 = (String)Java.call( dynamicModel, "createId" ); 

// 4) export .java & .class files:

//    export "C:\MyApp\src\main\java\mymodel\Model.java"

Export.dir( "C:\\MyApp\\src\\main\\java\\").toFile( _model );

//    export "C:\MyApp\traget\classes\mymodel\Model.class"

Export.dir( "C:\\MyApp\\target\\classes\\").toFile( dynamicModel.getClass() );

```

...```Export( "C:\\MyApp\\src\\main\\java\\").toFile( _model );``` will create the file ```C:\\myapp\\src\\main\\java\\mymodel\\Model.java``` containing:

```java

package mymodel;

import java.util.UUID;

public class Model

{

    public String createId(  )

    {

        return UUID.randomUUID().toString();

    }

}

```

## metaprogramming : read in existing code, modify it & run it ##

varcode makes **metaprogramming** easy. **load a  ```( _class, _enum, _interface, _annotationType )```** from an existing class, modify it at the source level, then compile & use it at runtime (no restarting required). 

```java

// 1. build the _class model from the .java source of the Class

_class _c = Java._classFrom( OriginalClass.class ); 

// 2. modify the model

_c.setName("Tailored");// change the class Name

_c.field("private static final int ID = 100;"); // add field

// get and modify the "toString" method

_c.getMethod("toString").body( "return getClass().getSimpleName() + ID;")

// 3. compile, instantiate and use it

Object tailored = _c.instance(); // create a new instance of "Tailored"

System.out.println( tailored );  //prints "Tailored100"

```

## construct classes step by step ##

classes for ( [\_class](https://gist.github.com/edefazio/b491989cd6ef72ad7ea2bc0005895c81), [\_interface](https://gist.github.com/edefazio/adbbd9cd500617d3202b2a2a3c7ebf68), [\_enum](https://gist.github.com/edefazio/0e566868ab5f134720cfde6db24b9b11), [\_annotationType](https://gist.github.com/edefazio/f1bed02ff66524149c215311c6d6f356) ) can be built in a single compound statement or incrementally using simple mutator methods. 

```java 

_class _c = _class.of( "package ex.mutable;",

    _imports.of( Serializable.class ),

    "@Deprecated",     

    "public class MyMutableModel implements Serializable" );

    

_method _m = _method.of( "/** create a random number */", 

    "@Generated",

    "public static final double random()", 

    "return Math.random();" );

    

_c.method( _m );   //add the "random" method to the _class  

    

_field _f = _field.of( "/** field javadoc */", 

    "public static int ID = 100;"); 

    

_c.add( _f ); //add the "ID" field to the _class

```