Springboot动态生成一个项目中没有的类（class对象） / 四六文摘

这两天新接到一个需求，是这样。从页面上文本写一个拦截器，然后上传这个拦截器的源码，生成对象并调用对象的方法。

我当时的反应就是很懵逼的。。。这个操作也太骚了吧

年前写了个用groovy来执行，但是会出现一些问题，不能满足需求。

年后开始重新思考这个问题，然后在网上找到了一篇资料

http://blog.sina.com.cn/s/blog_70279be20101dk0j.html

重点是找到了一个东西

jdk提供一个动态编译的类。JavaCompiler javac;

这样首先是解决了，将源码编译成为对应的class文件，接下来是动态加载class文件到项目中生成。这一步就通过类加载器来完成。

理清除思路后，我就开始做一个最简单的通过main方法执行生成一个动态类，然后将代码移植到springboot项目中。

import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import java.io.IOException;
import java.util.Arrays;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* @author: Bobby
* @create: 2020-02-11 15:29
* @description:动态执行
**/
public class DynamicLoader {
/**
* auto fill in the java-name with code, return null if cannot find the public class
*
* @param javaSrc source code string
* @return return the Map, the KEY means ClassName, the VALUE means bytecode.
*/
public static Map<String, byte[]> compile(String javaSrc) {
Pattern pattern = Pattern.compile("public\\s+class\\s+(\\w+)");
Matcher matcher = pattern.matcher(javaSrc);
if (matcher.find()) {
return compile(matcher.group(1) + ".java", javaSrc);
}
return null;
}
public static Map<String, byte[]> compile(String javaName, String javaSrc) {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager stdManager = compiler.getStandardFileManager(null, null, null);
try (MemoryJavaFileManager manager = new MemoryJavaFileManager(stdManager)) {
JavaFileObject javaFileObject = manager.makeStringSource(javaName, javaSrc);
JavaCompiler.CompilationTask task = compiler.getTask(null, manager, null, null, null, Arrays.asList(javaFileObject));
if (task.call())
return manager.getClassBytes();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}

import javax.tools.*;
import java.io.*;
import java.net.URI;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.CharBuffer;
import java.util.HashMap;
import java.util.Map;
/**
* @author: Bobby
* @create: 2020-02-11 16:10
* @description:
**/
public class MemoryClassLoader extends URLClassLoader {
Map<String, byte[]> classBytes = new HashMap<String, byte[]>();
public MemoryClassLoader(Map<String, byte[]> classBytes) {
super(new URL[0], MemoryClassLoader.class.getClassLoader());
this.classBytes.putAll(classBytes);
}
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
byte[] buf = classBytes.get(name);
if (buf == null) {
return super.findClass(name);
}
classBytes.remove(name);
return defineClass(name, buf, 0, buf.length);
}
}
/**
* * MemoryJavaFileManager.java
* JavaFileManager that keeps compiled .class bytes in memory.
*/
@SuppressWarnings("unchecked")
final class MemoryJavaFileManager extends ForwardingJavaFileManager {
/**
* Java source file extension.
*/
private final static String EXT = ".java";
private Map<String, byte[]> classBytes;
public MemoryJavaFileManager(JavaFileManager fileManager) {
super(fileManager);
classBytes = new HashMap<String, byte[]>();
}
public Map<String, byte[]> getClassBytes() {
return classBytes;
}
public void close() throws IOException {
classBytes = new HashMap<String, byte[]>();
}
public void flush() throws IOException {
}
/**
* A file object used to represent Java source coming from a string.
*/
private static class StringInputBuffer extends SimpleJavaFileObject {
final String code;
StringInputBuffer(String name, String code) {
super(toURI(name), Kind.SOURCE);
this.code = code;
}
public CharBuffer getCharContent(boolean ignoreEncodingErrors) {
return CharBuffer.wrap(code);
}
public Reader openReader() {
return new StringReader(code);
}
}
/**
* A file object that stores Java bytecode into the classBytes map.
*/
private class ClassOutputBuffer extends SimpleJavaFileObject {
private String name;
ClassOutputBuffer(String name) {
super(toURI(name), Kind.CLASS);
this.name = name;
}
public OutputStream openOutputStream() {
return new FilterOutputStream(new ByteArrayOutputStream()) {
public void close() throws IOException {
out.close();
ByteArrayOutputStream bos = (ByteArrayOutputStream) out;
classBytes.put(name, bos.toByteArray());
}
};
}
}
public JavaFileObject getJavaFileForOutput(Location location,
String className,
JavaFileObject.Kind kind,
FileObject sibling) throws IOException {
if (kind == JavaFileObject.Kind.CLASS) {
return new ClassOutputBuffer(className);
} else {
return super.getJavaFileForOutput(location, className, kind, sibling);
}
}
static JavaFileObject makeStringSource(String name, String code) {
return new StringInputBuffer(name, code);
}
static URI toURI(String name) {
File file = new File(name);
if (file.exists()) {
return file.toURI();
} else {
try {
final StringBuilder newUri = new StringBuilder();
newUri.append("mfm:///");
newUri.append(name.replace('.', '/'));
if (name.endsWith(EXT)) newUri.replace(newUri.length() - EXT.length(), newUri.length(), EXT);
return URI.create(newUri.toString());
} catch (Exception exp) {
return URI.create("mfm:///com/sun/script/java/java_source");
}
}
}
}

然后开始通过接口测试

import com.ocft.gateway.clazzloader.DynamicLoader;
import com.ocft.gateway.clazzloader.MemoryClassLoader;
import com.ocft.gateway.common.context.GatewayContext;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Iterator;
import java.util.Map;
import java.util.Random;
/**
* @author: Bobby
* @create: 2020-02-14 20:28
* @description:
**/
@RestController
@RequestMapping("/dynamicloader")
public class DynamicLoaderTestController {
private static String javaSrc = "public class TestClass{" +
"public void sayHello(String msg) {" +
"System.out.printf(\"Hello %s! This message from a Java String.%n\",msg);" +
"}" +
"public int add(int a,int b){" +
"return a+b;" +
"}" +
"}";
private static String javaSrcInterreptor=
"import com.alibaba.fastjson.JSONObject;\n" +
"import com.ocft.gateway.common.context.GatewayContext;\n" +
"import com.ocft.gateway.common.evaluator.JsonOperateEvalutor;\n" +
"import com.ocft.gateway.common.exceptions.GatewayException;\n" +
"import com.ocft.gateway.entity.GatewayInterface;\n" +
"import com.ocft.gateway.entity.InterfaceConfig;\n" +
"import com.ocft.gateway.entity.RequestAccessLimit;\n" +
"import com.ocft.gateway.entity.RequestType;\n" +
"import com.ocft.gateway.interceptor.GatewayInterceptor;\n" +
"import com.ocft.gateway.service.IInterfaceConfigService;\n" +
"import com.ocft.gateway.service.IRequestTypeService;\n" +
"import com.ocft.gateway.utils.MathUtil;\n" +
"import com.ocft.gateway.utils.RedisUtil;\n" +
"import com.ocft.gateway.utils.WebUtil;\n" +
"import lombok.extern.slf4j.Slf4j;\n" +
"import org.apache.commons.lang3.StringUtils;\n" +
"import org.slf4j.Logger;\n" +
"import org.slf4j.LoggerFactory;\n" +
"import org.springframework.beans.factory.annotation.Autowired;\n" +
"import org.springframework.stereotype.Component;\n" +
"import javax.servlet.http.HttpServletRequest;\n" +
"import java.util.Date;\n" +
"import java.util.List;" +
"@Slf4j\n" +
"@Component\n" +
"public class TestIntercept implements GatewayInterceptor {" +
" @Override\n" +
" public void doInterceptor(GatewayContext context) {" +
" System.out.printf(\"Hello Bobby\"); " +
" }" +
"}" +
"";
@RequestMapping("/test")
public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException {
Map<String, byte[]> bytecode = DynamicLoader.compile("TestIntercept.java", javaSrcInterreptor);
MemoryClassLoader classLoader = new MemoryClassLoader(bytecode);
Class clazz = classLoader.loadClass("TestIntercept");
Object object = clazz.newInstance();
Method doInterceptor = clazz.getMethod("doInterceptor", GatewayContext.class);
doInterceptor.invoke(object, new GatewayContext());
}
public void testCompile() {
Map<String, byte[]> bytecode = DynamicLoader.compile("TestClass.java", javaSrc);
for (Iterator<String> iterator = bytecode.keySet().iterator(); iterator.hasNext(); ) {
String key = iterator.next();
byte[] code = bytecode.get(key);
System.out.printf("Class: %s, Length: %d%n", key, code.length);
}
}

最后可以成功输出

Springboot动态生成一个项目中没有的类（class对象）

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