來源:http://www.bjsxt.com/
一、S02E214_01動態編譯_DynamicCompile、反射調用main方法問題
代碼測試:
public class HelloWorld {
public static void main(String[] args){
System.out.println("Hi!!!!");
}
}
package com.test.dynamicCompile;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
public class Demo {
public static void main(String[] args) throws IOException {
//1、通過JavaCompiler動態編譯
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
int result = compiler.run(null,null,null,"G:/JAVA/test/HelloWorld.java");
System.out.println(result==0?"編譯成功":"編譯失敗");
//通過IO流操作,將字符串存儲成一個臨時文件,然後調用動態編譯方法!
String str = "public class Hi { public static void main(String[] args){System.out.println(\"HAHA\");}}";
//此處省略一大段代碼。。。
//2、通過Runtime.getRuntime()運行啓動新的進程動態運行編譯好的類
Runtime run = Runtime.getRuntime();
Process process = run.exec("java -cp g:/java/test HelloWorld");
InputStream in = process.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String info = "";
while ((info=reader.readLine())!=null) {
System.out.println(info);
}
//3、通過反射運行編譯好的類
try {
URL[] urls = new URL[] {new URL("file:/" + "g:/java/test/")};
URLClassLoader loader = new URLClassLoader(urls);
Class c = loader.loadClass("HelloWorld");
//調用加載類的main方法
Method m = c.getMethod("main", String[].class);
m.invoke(null, (Object)new String[]{});
//m.invoke(null, new String[]{"a","b"});
//上面代碼會被編譯成:m.invoke(null,"a","b"),這樣就發生參數個數不匹配的問題
//因此,必須加上(Object)進行轉型,避免這個問題
} catch (Exception e) {
e.printStackTrace();
}
}
}
控制檯輸出
編譯成功
Hi!!!!
Hi!!!!