在java中动态执行一段代码

 

动态的执行一段简单代码，采用生成java文件，调用javac编译，反射执行的方式。

只是一个简单测试，有些地方有待完善。

代码如下

 

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import java.io.*;

/**
* 动态执行一段代码(生成文件->编译->执行)
* @author kingfish
* @version 1.0
*/
public class TestRun {
private String fileName = "Test.java";
private String className= "Test.class";
public TestRun() {
File f = new File(fileName);
if(f.exists()) f.delete();

f = new File(className);
if(f.exists()) f.delete();
}

/**
* 创建java文件
*/
public void createJavaFile(String body) {
String head = "public class Test{\r\n public static void runCode(){";

String end = "\r\n }\r\n}";
try {
DataOutputStream dos = new DataOutputStream(new FileOutputStream(
fileName));
dos.writeBytes(head);
dos.writeBytes(body);
dos.writeBytes(end);
dos.close();
}
catch (Exception e) {
e.printStackTrace();
}
}

/**
* 编译
*/
public int makeJavaFile() {
int ret = 0;
try {
Runtime rt = Runtime.getRuntime();
Process ps = rt.exec("cmd /c javac " + fileName);
ps.waitFor();
byte[] out = new byte[1024];
DataInputStream dos = new DataInputStream(ps.getInputStream());
dos.read(out);
String s = new String(out);
if (s.indexOf("Exception") > 0) {
ret = -1;
}
}
catch (Exception e) {
ret = -1;
e.printStackTrace();
}
return ret;
}

/**
* 反射执行
*/
public void run() {
try {
Class.forName("Test").getMethod("runCode", new Class[] {}).invoke(null, new Object[]{});
}
catch (Exception e) {
e.printStackTrace();
}
}

/**
* 测试
*/
public static void main(String[] args) {

String cmd = "System.out.println(\"usage:java TestRun int i=1; System.out.println(i+100);\");";
if(args.length>=1){
cmd = args[0];
}
TestRun t = new TestRun();
t.createJavaFile(cmd);
if (t.makeJavaFile() == 0) {
t.run();
}
}
}

 

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测试：

java TestRun System.out.println(\"Hello,World!\");

java TestRun "int i=1;int j=2;System.out.println(i+j);"