java 动态编译运行

矫情吗；* 2023-10-08 17:14 57阅读 0赞

#### 文章目录 ####

*  写在前面
 *   *  1、Java Compiler
     *   *  1.1、java文件编译成class文件
         *   *  run 编译
             *  exec 执行指令
         *  1.2、字符串编译成class文件
         *  1.3、工具类

## 写在前面 ##

Java Compiler 可以动态执行一段字符串形式的java代码，或手动编译java文件。

### 1、Java Compiler ###

#### 1.1、java文件编译成class文件 ####

##### run 编译 #####

D:\\Test.java 文件内容：

public class Test {
        
        public static void main(String[] args) {
        
    		int i = 0;
            System.out.println("test run "+i);
        }
    }

把java文件编译成class文件

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
            int result = compiler.run(null, null, null, "D:\\Test.java");   // 在 D:\\Test.java 同目录下，会出现Test.class文件
            System.out.println(result == 0 ? "编译成功" : "编译失败");

##### exec 执行指令 #####

exec 执行指令，等同于在cmd中输入指令

// 执行java命令,空参数,所在文件夹
            Process process = Runtime.getRuntime().exec("java Test", null, new File("F:\\demo\\"));
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            String str;
            while ((str = bufferedReader.readLine()) != null) {
        
                System.out.println(str);    // 这里打印的是控制台输出的
            }

如上代码，等同于在cmd输入：java Test

![在这里插入图片描述][6c1ead7f196643ee858df97bf077ee84.png]

#### 1.2、字符串编译成class文件 ####

新建类 StringObject，代表字符串java对象内容

package com.kaka;
    
    import javax.tools.SimpleJavaFileObject;
    import java.io.IOException;
    import java.net.URI;
    import java.net.URISyntaxException;
    
    // 必须继承自SimpleJavaFileObject 
    public class StringObject extends SimpleJavaFileObject {
        
        private String content = null;
    
        protected StringObject(String className, String contents) throws URISyntaxException {
        
            super(new URI(className), Kind.SOURCE);
            this.content = contents;
        }
    
        @Override
        public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
        
            return content;
        }
    }

编译java字符串

package com.kaka;
    
    import javax.tools.*;
    import java.net.URISyntaxException;
    import java.util.Collections;
    
    public class Test01 {
        
    
        public static void main(String[] args) throws URISyntaxException {
        
            // 要编译的字符串,这个字符串必须是一个类
            String contents = "package com.kaka;" +
                    "class Test {\n" +
                    "    public static void main(String[] args) {\n" +
                    "\tint i = 0;\n" +
                    "        System.out.println(\"测试运行 \"+i);\n" +
                    "    }\n" +
                    "}";
    
            JavaCompiler javaCompiler = ToolProvider.getSystemJavaCompiler();
            StandardJavaFileManager standardJavaFileManager = javaCompiler.getStandardFileManager(null, null, null);
            JavaFileObject testFile = new StringObject("com.kaka.Test", contents);
            JavaCompiler.CompilationTask task = javaCompiler.getTask(null, standardJavaFileManager, null, null, null, Collections.singletonList(testFile));
            if(task.call()){
        
                System.out.println("success");
            }else{
        
                System.out.println("failure!");
            }
        }
    }

#### 1.3、工具类 ####

将1.1和1.2总结为一个工具类

package com;
    
    import javax.tools.*;
    import java.io.BufferedReader;
    import java.io.File;
    import java.io.FileReader;
    import java.io.IOException;
    import java.lang.reflect.Method;
    import java.net.URI;
    import java.util.Arrays;
    import java.util.Collections;
    import java.util.List;
    
    public class JavaCodeUtil {
        
        /** java字符串代码，转为class文件 **/
        public static String codeToClass(String code,String compilePath) {
        
            String className = getClassNameFromCode(code);
            JavaCompiler javaCompiler = ToolProvider.getSystemJavaCompiler();
            StandardJavaFileManager fileManager = javaCompiler.getStandardFileManager(null, null, null);
            JavaFileObject stringObject = new StringObject(className, code);
            // compilePath 指定编译的class文件的路径
            List<String> options = Arrays.asList("-d", compilePath);
            JavaCompiler.CompilationTask task = javaCompiler.getTask(null, fileManager, null, options, null, Collections.singletonList(stringObject));
            if(task.call()){
        
                // 从code第一行读出包名
                String packageName = getPackageNameInFirstLine(code);
                String classFileName = className + "." + "class";
                return compilePath + "/" +  packageName + "/" + classFileName;
            }else{
        
                return null;
            }
        }
    
        public static String javaToClass(String fileName,String compilePath) throws IOException {
        
            JavaCompiler javaCompiler = ToolProvider.getSystemJavaCompiler();
            StandardJavaFileManager fileManager = javaCompiler.getStandardFileManager(null, null, null);
            Iterable<? extends JavaFileObject> fileObjects = fileManager.getJavaFileObjects(fileName);
            // compilePath 指定编译的class文件的路径
            List<String> options = Arrays.asList("-d", compilePath);
            JavaCompiler.CompilationTask task = javaCompiler.getTask(null, fileManager, null, options, null, fileObjects);
            if(task.call()){
        
                // 从文件第一行读包名
                File sourceFile = new File(fileName);
                BufferedReader bufferedReader = new BufferedReader(new FileReader(sourceFile));
                String line;
                while ((line = bufferedReader.readLine()) != null) {
        
                    if (line.startsWith("package")) {
        
                        break;
                    }
                }
                String packageName = line;
                packageName = packageName.replaceAll("package", "").trim().replaceAll("\\.", "/");
                packageName = packageName.substring(0, packageName.length() - 1);
    
                // 获取类名（这里简单处理, 默认文件名与类名相同）
                String sourceFileName = sourceFile.getName();
    
                String[] split = sourceFileName.split("\\.");
                String simpleClassName = split[0] + "." + "class";
    
                return compilePath + "/" +  packageName + "/" + simpleClassName;
            }else{
        
                return null;
            }
        }
    
        public static class StringObject extends SimpleJavaFileObject {
        
            private final String content;
            public StringObject(String className, String contents) {
        
                super(URI.create(className), Kind.SOURCE);
                this.content = contents;
            }
            @Override
            public CharSequence getCharContent(boolean ignoreEncodingErrors){
        
                return content;
            }
        }
    
        /** 根据java文件第一行获取包名 */
        public static String getPackageNameInFirstLine(String code){
        
            return code
                    .substring(0,code.indexOf(";"))
                    .replace("package ", "")
                    .replaceAll("\\.", "/");
        }
    
        /** 从java String字符串中获取类名 */
        public static String getClassNameFromCode(String code){
        
            int classBlank = code.indexOf("class ")+6;
            String className = code.substring(classBlank);
            int nextBlank = className.indexOf(" ");
            className = className.substring(0,nextBlank);
            if(className.contains("{")){
        
                int i = className.indexOf("{");
                className = className.substring(0,i);
            }
            return className;
        }
    
        /** 获取项目根目录 */
        public static String getProjectPath() {
        
            String path = JavaCodeUtil.class.getProtectionDomain().getCodeSource().getLocation().getPath();
            if (System.getProperty("os.name").contains("dows")) {
        
                path = path.substring(1);
            }
    
            if (path.contains("jar")) {
        
                path = path.substring(0, path.lastIndexOf("."))
                        .substring(0, path.lastIndexOf("/"));
                return path;
            } else {
        
                return path.replace("target/classes/", "");
            }
        }
    }

测试使用JavaCodeUtil

public static void main(String[] args) throws ClassNotFoundException {
        
            // java代码
            String contents = "package com.kaka;\n" +
                    "class Test02 {\n" +
                    "    public static void main(String[] args) {\n" +
                    "\tint i = 0;\n" +
                    "        System.out.println(\"这是Test02的main方法 \"+i);\n" +
                    "    }\n" +
                    "   public void getiii(){}\n" +
                    "}";
            
            // 把字符串编译成class文件
            JavaCodeUtil.codeToClass(contents,getProjectPath()+"target/classes");
            // 加载这个calss文件
            Class<?> aClass = Class.forName("com.kaka.Test02");
            // 获取Test02中的方法
            Method[] methods = aClass.getMethods();
            for (Method method : methods) {
        
                System.out.println(method.getName());
            }
        }

[6c1ead7f196643ee858df97bf077ee84.png]: https://img-blog.csdnimg.cn/6c1ead7f196643ee858df97bf077ee84.png