如何使用flink动态加载类
时间: 2024-05-11 12:14:26 浏览: 12
Flink动态加载类可以通过以下步骤实现:
1. 创建一个实现了接口org.apache.flink.api.common.functions.RuntimeContext的类,该类用于提供类加载器和类路径信息。
2. 在Flink程序中创建一个动态类加载器,该加载器从提供类加载器的类中获取类加载器和类路径信息,并使用Java反射机制动态加载类。
3. 在Flink程序中使用动态类加载器加载需要动态加载的类。
下面是一个简单的示例代码:
```
public class CustomContext implements RuntimeContext {
private ClassLoader classLoader;
private String[] classpath;
public CustomContext(ClassLoader classLoader, String[] classpath) {
this.classLoader = classLoader;
this.classpath = classpath;
}
@Override
public ClassLoader getUserCodeClassLoader() {
return classLoader;
}
@Override
public String[] getDistributedCacheEntries() {
return new String[0];
}
@Override
public String getTaskName() {
return null;
}
@Override
public int getNumberOfParallelSubtasks() {
return 0;
}
@Override
public int getIndexOfThisSubtask() {
return 0;
}
}
public class DynamicClassLoader extends ClassLoader {
private CustomContext context;
public DynamicClassLoader(CustomContext context) {
this.context = context;
}
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
try {
byte[] bytes = loadClassData(name);
return defineClass(name, bytes, 0, bytes.length);
} catch (IOException e) {
throw new ClassNotFoundException(name);
}
}
private byte[] loadClassData(String name) throws IOException, ClassNotFoundException {
String path = name.replace('.', '/') + ".class";
InputStream stream = context.getUserCodeClassLoader().getResourceAsStream(path);
if (stream == null) {
throw new ClassNotFoundException(name);
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int read;
while ((read = stream.read(buffer)) != -1) {
out.write(buffer, 0, read);
}
stream.close();
return out.toByteArray();
}
}
public class DynamicClassLoadingExample {
public static void main(String[] args) throws Exception {
String className = "com.example.MyFunction";
CustomContext context = new CustomContext(DynamicClassLoadingExample.class.getClassLoader(), System.getProperty("java.class.path").split(":"));
DynamicClassLoader loader = new DynamicClassLoader(context);
Class<?> clazz = loader.loadClass(className);
Function function = (Function) clazz.newInstance();
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
DataStream<String> stream = env.socketTextStream("localhost", 9999);
stream.map(function).print();
env.execute();
}
}
```
在示例代码中,CustomContext类实现了RuntimeContext接口,并提供了类加载器和类路径信息。DynamicClassLoader类继承了ClassLoader类,并使用CustomContext类提供的类加载器和类路径信息动态加载类。DynamicClassLoadingExample类使用动态类加载器加载需要动态加载的类,并在Flink程序中使用该类。