动态编译-在线Java编译运行例子

蔚落 2021-06-24 16:00 568阅读 0赞

[https://www.cnblogs.com/hujunzheng/p/5203067.html][https_www.cnblogs.com_hujunzheng_p_5203067.html]

首先简单介绍一下思路：

1.得到java程序的源代码，不需要导入包。得到源码之后在前面加入”import java.util.\*;”

2.通过JavaCompiler对象可以帮助我们将java源代码编译成class文件。

3.通过DiagnosticCollector对象可以获得编译过程中产生的编译信息。

4.通过StandardJavaFileManager对象管理生成的class文件，例如文件的存放位置。

5.StringSourceJavaObject对象可以对java源码进行包装并处理。

数据是控制台输入的，所以要重定向System.in(注意保存标准的输入流)；另外程序的输出是到标准的输出流的，为了获得输出结果，我的方法是重定向输出流到ByteArrayOutputStream，然后利用ByteArrayOutputStream构造BufferedReader。

6.运行程序，通过java的反射机制，获得main函数的Method对象。

7.运行时间的计算: 通过System.currentTimeMillis()方法。

8.程序所需内存: 通过Runtime的freeMemory()方法。

9.异常信息的获取：StringWriter sw = new StringWriter();  e.printStackTrace(new PrintWriter(sw, true)); sw.toString();

遇到的问题：

1. JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); 出现NullPointerException。

查看部分源码如下：

private static final String[] defaultToolsLocation = { "lib", "tools.jar" };
    private Class<?> findSystemToolClass(String toolClassName)
            throws MalformedURLException, ClassNotFoundException {
        // try loading class directly, in case tool is on the bootclasspath
        try {
            return Class.forName(toolClassName, false, null);
        } catch (ClassNotFoundException e) {
            trace(FINE, e);
    
            // if tool not on bootclasspath, look in default tools location (tools.jar)
            ClassLoader cl = (refToolClassLoader == null ? null : refToolClassLoader.get());
            if (cl == null) {
                File file = new File(System.getProperty("java.home"));
                if (file.getName().equalsIgnoreCase("jre"))
                    file = file.getParentFile();
                for (String name : defaultToolsLocation)
                    file = new File(file, name);
    
                // if tools not found, no point in trying a URLClassLoader
                // so rethrow the original exception.
                if (!file.exists())
                    throw e;
    
                URL[] urls = { file.toURI().toURL() };
                trace(FINE, urls[0].toString());
    
                cl = URLClassLoader.newInstance(urls);
                refToolClassLoader = new WeakReference<ClassLoader>(cl);
            }
    
            return Class.forName(toolClassName, false, cl);
        }
    }

打印 System.out.println(System.getProperty("java.home")); 如下：

C:\\Program Files (x86)\\Java\\jre6

defaultToolsLocation = \{ "lib", "tools.jar" \}; 也就是最终到

C:\\Program Files (x86)\\Java\\jre6\\lib\\tools.jar中寻找tools.jar

然而jre6\\lib中没有tools.jar, 而是在C:\\Program Files (x86)\\Java\\jdk\\lib中。最直接的办法就是将它复制进去就行了。

2.异常信息的获取。

3.输入流和输出流的重定向。

详细内容请看代码!

import java.io.BufferedReader;
    import java.io.ByteArrayInputStream;
    import java.io.ByteArrayOutputStream;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileReader;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.io.PrintStream;
    import java.io.PrintWriter;
    import java.io.StringWriter;
    import java.lang.reflect.Method;
    import java.net.URI;
    import java.util.Arrays;
    import java.util.regex.Matcher;
    import java.util.regex.Pattern;
    
    import javax.tools.Diagnostic;
    import javax.tools.DiagnosticCollector;
    import javax.tools.JavaCompiler;
    import javax.tools.JavaCompiler.CompilationTask;
    import javax.tools.JavaFileObject;
    import javax.tools.SimpleJavaFileObject;
    import javax.tools.StandardJavaFileManager;
    import javax.tools.StandardLocation;
    import javax.tools.ToolProvider;
    
    public class CompileAndRunJavaFile {
        public static void main(String[] args) {
            StringBuilder code = new StringBuilder();
            try {
                BufferedReader br = new BufferedReader(new FileReader(new File("测试程序地址")));
                String content;
                while((content = br.readLine()) != null){
                    code.append(content).append("\n");
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            CompileAndRunJavaFile cr = new CompileAndRunJavaFile();
            cr.compileAndRunJavaFile(code.toString());
            if(cr.isCompileAndRunOK()) {
                System.out.println("运行时间: " + cr.getUseTime() + "ms");
                System.out.println("内存使用: " + cr.getUseMemory() + "kb9");
                System.out.println("运行结果: \n" + cr.getOutMsg());
            } else if(cr.isCompilerError()) {
                System.out.println("编译错误: " + cr.getCE());
            } else if(cr.isRunningError()) {
                System.out.println("运行错误: " + cr.getError());
            }
        }
        //编译错误
        private StringBuilder ce = new StringBuilder();
        public String getCE(){
            return ce.toString();
        }
        
        //内存使用
        private double useMemory = 0.0;
        public double getUseMemory(){
            return useMemory;
        }
        
        //运行时间
        private long useTime = 0;
        public long getUseTime(){
            return useTime;
        }
        //输出信息
        private StringBuilder outMsg = new StringBuilder();
        public String getOutMsg(){
            return outMsg.toString();
        }
        //异常信息
        private String error = null;
        public String getError(){
            return error;
        }
        //是否正常编译并运行
        private boolean isCompileAndRunOK = false; 
        
        public boolean isCompileAndRunOK(){
            return isCompileAndRunOK;
        }
        
        //程序的运行时间, 单位：ms
        private int limitTime = 2000;
        //程序所占内存, 单位 ：KB
        private double limitMemory = 256000.0;
        
        public void setLimitTime(int limitTime){
            this.limitTime = limitTime;
        }
        
        public void setLimitMemory(double limitMemory){
            this.limitMemory = limitMemory;
        }
        
        //是否为编译错误
        private boolean isCompilerError = false;
        public boolean isCompilerError(){
            return isCompilerError;
        }
        
        //是否为运行错误
        private boolean isRunningError = false;
        public boolean isRunningError(){
            return isRunningError;
        }
        
        private static final String className = "Main";
        private static final String methodName = "main";
        private String getClassOutput(){
            //设置class文件的存放位置
            if(System.getProperty("java.class.path").contains("bin")) return "bin/";
            else return "./";
        }
        
        private void compileAndRunJavaFile(String code){
            PrintStream ps = null;
            FileInputStream fis = null;
            BufferedReader br = null;
            //保存标准输出流
            InputStream stdIn = System.in;
            //保存标准输入流
            PrintStream stdOut = System.out;
            
            //为源代码导入默认的包
            code = "import java.util.*;\n" + code;
            try {
                JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
                // define the diagnostic object, which will be used to save the
                // diagnostic information
                DiagnosticCollector<JavaFileObject> oDiagnosticCollector = new DiagnosticCollector<JavaFileObject>();
                StandardJavaFileManager fileManager = compiler.getStandardFileManager(oDiagnosticCollector, null, null);
                // set class output location
                fileManager.setLocation(StandardLocation.CLASS_OUTPUT, Arrays.asList(new File[] { new File(getClassOutput()) }));
                
                StringSourceJavaObject sourceObject = new CompileAndRunJavaFile.StringSourceJavaObject(className, code);
                Iterable<? extends JavaFileObject> fileObjects = Arrays.asList(sourceObject);
                CompilationTask task = compiler.getTask(null, fileManager, oDiagnosticCollector, null, null, fileObjects);
                boolean result = task.call();
                
                if (result) {
                    Runtime runtime = Runtime.getRuntime();
                    Class<?> clazz = Class.forName(className);
                    Method method = clazz.getMethod(methodName, new Class<?>[]{String[].class});
                    
                    //重置输入流， 需要存放数据文件的文件名
                    fis = new FileInputStream(new File("数据文件地址"));
                    System.setIn(fis);
                    //重置输出流，需要获得控制台的输出
                    ByteArrayOutputStream bao = new ByteArrayOutputStream();
                    ps = new PrintStream(bao);
                    System.setOut(ps);
                    
                    long startFreeMemory = runtime.freeMemory();//Java 虚拟机中的空闲内存量
                    //执行时间也是无法知道，因为dos执行java命令，程序无法知道它到底执行到那里了，两个进程，互不了解
                    long startCurrentTime = System.currentTimeMillis();//获取系统当前时间
                    method.invoke(null, new Object[]{null});
                    long endCurrentTime = System.currentTimeMillis();
                    long endFreeMemory = runtime.freeMemory();
                    //内存的使用情况，不是很精确
                    useMemory = (startFreeMemory-endFreeMemory)/1024.0;
                    if(useMemory > limitMemory) throw new Exception("Out Limit Memory!");
                    useTime = endCurrentTime-startCurrentTime;
                    if(useTime > limitTime) throw new Exception("Time Limited!");
                    
                    //获得控制台的输出
                    br = new BufferedReader(new InputStreamReader(new ByteArrayInputStream(bao.toByteArray())));
                    String outc = null;
                    while((outc = br.readLine()) != null)
                        outMsg.append(outc).append("\n");
                    //正常编译并运行
                    isCompileAndRunOK = true;
                } else {
                    isCompilerError = true;
                    //打印编译的错误信息
                    Pattern p = Pattern.compile("Main.java\\D*(\\d+):", Pattern.DOTALL);
                    for (Diagnostic<? extends JavaFileObject> oDiagnostic : oDiagnosticCollector.getDiagnostics()){
                        /*信息示例：
                          Compiler Error: Main.java:8: 找不到符号
                             符号： 类 Scanner
                                    位置： 类 Main
                        */
                        //将行号减1
                        Matcher m = p.matcher("Compiler Error: " + oDiagnostic.getMessage(null));
                        if(m.find()) {
                            ce.append(m.replaceAll("Main.java " + String.valueOf(Integer.valueOf(m.group(1))-1)) + ":").append("\n");
                        } else {
                            ce.append("Compiler Error: " + oDiagnostic.getMessage(null)).append("\n");
                        }
                    }
                }
                
            } catch (Exception e) {
                isRunningError = true;
                StringWriter sw = new StringWriter();
                e.printStackTrace(new PrintWriter(sw, true));
                Pattern p = Pattern.compile("Main.java\\D*(\\d+)", Pattern.DOTALL);
                Matcher m = p.matcher(sw.toString());
                if(m.find()){
                    error = m.replaceAll("Main.java " + String.valueOf(Integer.valueOf(m.group(1))-1) + ":");
                } else {
                    error = sw.toString();
                }
            } finally {
                //关闭流
                try {
                    if(fis != null)
                        fis.close();
                    if(ps != null)
                        ps.close();    
                    if(br != null)
                        br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                //恢复输入输出流
                System.setIn(stdIn);
                System.setOut(stdOut);
            }
        }
        
        private class StringSourceJavaObject extends SimpleJavaFileObject {
            private String content = null;
            public StringSourceJavaObject(String name, String content) {
                super(URI.create(name.replace('.', '/') + Kind.SOURCE.extension), Kind.SOURCE);
                this.content = content;
            }
            public CharSequence getCharContent(boolean ignoreEncodingErrors) {
                return content;
            }
        }
    }

运行结果：

**1.正常运行**

运行时间: 16ms

内存使用: 225.5546875kb

运行结果:

5 4 3 2 1

**2.编译错误**

编译错误: Compiler Error: Main.java 8 找不到符号

符号： 类 Scanner

位置： 类 Main:

Compiler Error: Main.java 8 找不到符号

符号： 类 Scanner

位置： 类 Main:

**3.运行错误**

(1)运行错误: java.lang.reflect.InvocationTargetException

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

at java.lang.reflect.Method.invoke(Unknown Source)

at com.test.CompileAndRunJavaFile.compileAndRunJavaFile(CompileAndRunJavaFile.java:163)

at com.test.CompileAndRunJavaFile.main(CompileAndRunJavaFile.java:44)

Caused by: java.lang.StackOverflowError

at Main.fun(Main.java 4:)

**(2)运行错误**: java.lang.reflect.InvocationTargetException

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

at java.lang.reflect.Method.invoke(Unknown Source)

at com.test.CompileAndRunJavaFile.compileAndRunJavaFile(CompileAndRunJavaFile.java:163)

at com.test.CompileAndRunJavaFile.main(CompileAndRunJavaFile.java:44)

Caused by: java.lang.ArrayIndexOutOfBoundsException: 6

at Main.main(Main.java 18:)

... 6 more

demo：

public class Main {
        public static void fun(){
            fun();
        }
        public static void main(String[] args) {
    
            Scanner scan = new Scanner(System.in);
            int n = scan.nextInt();
            int[] array = new int[n];
            for(int i=0; i<n; ++i)
                array[i] = scan.nextInt();
            
            for(int i=0; i<n; ++i)
                System.out.print(array[i] + " ");
            System.out.println();
            
            //array[n+1] = 0;
            //fun();
        }
     
    }

[https_www.cnblogs.com_hujunzheng_p_5203067.html]: https://www.cnblogs.com/hujunzheng/p/5203067.html