Executing stringified source code in Java
Tags: java, tutorial, programming, generation
Published: 2020-12-08 20:38:51

Executing stringified source code in Java is hard to realize with only jdk core libraries but, if we are going to use the **CodeExecutor** of [**Burningwave Core**](https://burningwave.github.io/core/), the task will become simple and we can accomplish it in one of three different ways that we can choose:
* through BodySourceGenerator
* through a property located in Burningwave configuration file
* through a property located in a custom Properties file

**To use the CodeExecutor you should simply add the following to your projects dependencies**:

{% gist https://gist.github.com/Roberto-Gentili/536ee2d3f775030d46d82a008da10dbe.js %}

## **Executing code with BodySourceGenerator**
For the first way, we must create a **ExecuteConfig** by using the within static method **forBodySourceGenerator** to which must be passed the **BodySourceGenerator** that contains the source code with the parameters used within: after that we must pass the created configuration to the **execute** method of CodeExecutor as shown below:
```java
import java.util.ArrayList;
import java.util.List;

import org.burningwave.core.assembler.ComponentContainer;
import org.burningwave.core.assembler.ComponentSupplier;
import org.burningwave.core.classes.ExecuteConfig;
import org.burningwave.core.classes.BodySourceGenerator;

public class SourceCodeExecutor {
    
    public static Integer execute() {
        ComponentSupplier componentSupplier = ComponentContainer.getInstance();
        return componentSupplier.getCodeExecutor().execute(
            ExecuteConfig.forBodySourceGenerator(
                BodySourceGenerator.createSimple().useType(ArrayList.class, List.class)
                .addCodeLine("System.out.println(\"number to add: \" + parameter[0]);")
                .addCodeLine("List<Integer> numbers = new ArrayList<>();")
                .addCodeLine("numbers.add((Integer)parameter[0]);")
                .addCodeLine("System.out.println(\"number list size: \" + numbers.size());")
                .addCodeLine("System.out.println(\"number in the list: \" + numbers.get(0));")
                .addCodeLine("Integer inputNumber = (Integer)parameter[0];")
                .addCodeLine("return (T)new Integer(inputNumber + (Integer)parameter[1]);")
            ).withParameter(Integer.valueOf(5), Integer.valueOf(3))
        );
        
    }
    
    public static void main(String[] args) {
        System.out.println("Total is: " + execute());
    }
}
```
## **Executing code of a property located in Burningwave configuration file**
To execute code from Burningwave configuration file ([**burningwave.properties**](https://github.com/burningwave/core#configuration-1) or another file that we have used to create the [**ComponentContainer**](https://github.com/burningwave/core#dynamic-component-container): [see architectural overview and configuration](https://github.com/burningwave/core#Architectural-overview-and-configuration)) we must add to it a property that contains the code and, if it is necessary to import classes, you must add them to another property named as the property that contains the code plus the suffix ‘imports’. E.g:
```properties
code-block-1=\
	Date now= new Date();\
	return (T)now;
code-block-1.imports=java.util.Date;
```
It is also possible to include the code of a property in another property:
```properties
code-block-1=\
  ${code-block-2}\
  return (T)Date.from(zonedDateTime.toInstant());
code-block-1.imports=\
  ${code-block-2.imports};\
  java.util.Date;
code-block-2=\
  LocalDateTime localDateTime = (LocalDateTime)parameter[0];\
  ZonedDateTime zonedDateTime = localDateTime.atZone(ZoneId.systemDefault());
code-block-2.imports=\
  static org.burningwave.core.assembler.StaticComponentContainer.Strings;\
  java.time.LocalDateTime;\
  java.time.ZonedDateTime;\
  java.time.ZoneId;
```
After that, for executing the code of the property we must call the **executeProperty** method of CodeExecutor and passing to it the property name to be executed and the parameters used in the property code:
```java
import java.time.LocalDateTime;

import org.burningwave.core.assembler.ComponentContainer;
import org.burningwave.core.assembler.ComponentSupplier;

public class SourceCodeExecutor {
    
    public static void execute() {
        ComponentSupplier componentSupplier = ComponentContainer.getInstance();
        System.out.println("Time is: " +
            componentSupplier.getCodeExecutor().executeProperty("code-block-1", LocalDateTime.now())    
        );
    }
    
    public static void main(String[] args) {
        execute();
    }
}
```
## **Executing code of a property located in a custom properties file**

To execute code from a custom properties file we must add to it a property that contains the code and, if it is necessary to import classes, we must add them to another property named as the property that contains the code plus the suffix ‘**imports**’. E.g:

```properties
code-block-1=\
	Date now= new Date();\
	return (T)now;
code-block-1.imports=java.util.Date;
```

It is also possible to include the code of a property in another property:

```properties
code-block-1=\
  ${code-block-2}\
  return (T)Date.from(zonedDateTime.toInstant());
code-block-1.imports=\
  ${code-block-2.imports};\
  java.util.Date;
code-block-2=\
  LocalDateTime localDateTime = (LocalDateTime)parameter[0];\
  ZonedDateTime zonedDateTime = localDateTime.atZone(ZoneId.systemDefault());
code-block-2.imports=\
  static org.burningwave.core.assembler.StaticComponentContainer.Strings;\
  java.time.LocalDateTime;\
  java.time.ZonedDateTime;\
  java.time.ZoneId;
```

After that, for executing the code of the property we must create an **ExecuteConfig** object and set on it:
* the path (relative or absolute) of our custom properties file
* the property name to be executed
* the parameters used in the property code
Then we must call the **execute** method of CodeExecutor with the created ExecuteConfig object:

```java
import java.time.LocalDateTime;

import org.burningwave.core.assembler.ComponentContainer;
import org.burningwave.core.assembler.ComponentSupplier;
import org.burningwave.core.classes.ExecuteConfig;

public class SourceCodeExecutor {
    
    public static void execute() {
        ComponentSupplier componentSupplier = ComponentContainer.getInstance();
        System.out.println("Time is: " +
            componentSupplier.getCodeExecutor().execute(
                ExecuteConfig.forPropertiesFile("custom-folder/code.properties")
                //Uncomment the line below if the path you have supplied is an absolute path
                //.setFilePathAsAbsolute(true)
                .setPropertyName("code-block-1")
                .withParameter(LocalDateTime.now())
            )    
        );
    }
    
    public static void main(String[] args) {
        execute();
    }
}
```