Java 运行时动态生成类（动态编译）

我们有一个Person类：

package test;

import lombok.Data;

@Data
public abstract class Person {

    private String name;

    public abstract void sayHello();
}

Person类有一个抽象方法 sayHello，但是具体有哪些Person并不知道，需要配置在数据库中，然后动态进行生成Person的子类。

    com.itranswarp
    compiler
    1.0

如果是SpringBoot项目，最好加上

    com.sun
    tools
    1.8
    system
    ${java.home}/../lib/tools.jar

工具类代码如下：

package test;

import com.itranswarp.compiler.JavaStringCompiler;

import java.util.Map;

public class CompilerUtil {

    public static Class generateClass(String javaFilename, String packageName, String javaCode) throws Exception {

        JavaStringCompiler compiler = new JavaStringCompiler();

        String prefix = String.format("package %s;", packageName);

        Map map = compiler.compile(javaFilename + ".java", prefix + "n" + javaCode);

        return compiler.loadClass(packageName + "." + javaFilename, map);
    }
}

package test;

import com.itranswarp.compiler.JavaStringCompiler;

import java.util.Map;

public class CompilerUtil {

    public static Class generateClass(String javaFilename, String packageName, String javaCode) throws Exception {

        JavaStringCompiler compiler = new JavaStringCompiler();

        String prefix = String.format("package %s;", packageName);

        Map map = compiler.compile(javaFilename + ".java", prefix + "n" + javaCode);

        return compiler.loadClass(packageName + "." + javaFilename, map);
    }

    public static void main(String[] args) throws Exception {
        String teacherCode = "public class Teacher extends Person {n" +
                "n" +
                "    @Overriden" +
                "    public void sayHello() {n" +
                "        System.out.println("My name is " + getName() + ", I am a teacher");n" +
                "    }n" +
                "}n";

        Class teacherClass = generateClass("Teacher", "test", teacherCode);
        Person person = (Person) teacherClass.newInstance();
        person.setName("Tom");
        person.sayHello();
    }
}

My name is Tom, I am a teacher