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本文主要研究一下maxwell的Scripting
Scripting
maxwell-1.25.1/src/main/java/com/zendesk/maxwell/scripting/Scripting.java
public class Scripting {
static final Logger LOGGER = LoggerFactory.getLogger(Scripting.class);
private final ScriptObjectMirror processRowFunc, processHeartbeatFunc, processDDLFunc;
private ScriptObjectMirror getFunc(ScriptEngine engine, String fName, String filename) {
ScriptObjectMirror f = (ScriptObjectMirror) engine.get(fName);
if ( f == null )
return null;
else if ( !f.isFunction() ) {
throw new RuntimeException("Expected " + fName + " to be a function!");
} else {
LOGGER.info("using function " + fName + " from " + filename);
}
return f;
}
public Scripting(String filename) throws IOException, ScriptException, NoSuchMethodException {
ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("nashorn");
String externJS = new String(Files.readAllBytes(Paths.get(filename)));
engine.put("logger", LOGGER);
engine.eval(externJS);
processRowFunc = getFunc(engine, "process_row", filename);
processHeartbeatFunc = getFunc(engine, "process_heartbeat", filename);
processDDLFunc = getFunc(engine, "process_ddl", filename);
if ( processRowFunc == null && processHeartbeatFunc == null && processDDLFunc == null )
LOGGER.warn("expected " + filename + " to define at least one of: process_row,process_heartbeat,process_ddl");
}
public void invoke(RowMap row) {
if ( row instanceof HeartbeatRowMap && processHeartbeatFunc != null )
processHeartbeatFunc.call(null, new WrappedHeartbeatMap((HeartbeatRowMap) row));
else if ( row instanceof DDLMap && processDDLFunc != null )
processDDLFunc.call(null, new WrappedDDLMap((DDLMap) row));
else if ( row instanceof RowMap && processRowFunc != null )
processRowFunc.call(null, new WrappedRowMap(row));
}
private static ThreadLocal<ScriptEngine> stringifyEngineThreadLocal = ThreadLocal.withInitial(() -> {
ScriptEngineManager manager = new ScriptEngineManager();
return manager.getEngineByName("nashorn");
});
public static String stringify(ScriptObjectMirror mirror) throws ScriptException {
ScriptObjectMirror json = (ScriptObjectMirror) stringifyEngineThreadLocal.get().eval("JSON");
return (String) json.callMember("stringify", mirror);
}
}
- Scripting定义了processRowFunc、processHeartbeatFunc、processDDLFunc属性;其构造器接收filename参数,它创建ScriptEngineManager,然后获取名为nashorn的ScriptEngine,之后通过filename获取externJS,并执行engine.eval(externJS),之后通过getFunc方法初始化化processRowFunc、processHeartbeatFunc、processDDLFunc;其getFunc方法通过engine.get(fName)获取ScriptObjectMirror;其invoke方法针对HeartbeatRowMap执行processHeartbeatFunc.call,针对DDLMap执行processDDLFunc.call,针对RowMap执行processRowFunc.call
MaxwellConfig
maxwell-1.25.1/src/main/java/com/zendesk/maxwell/MaxwellConfig.java
public class MaxwellConfig extends AbstractConfig {
static final Logger LOGGER = LoggerFactory.getLogger(MaxwellConfig.class);
//......
public String javascriptFile;
public Scripting scripting;
//......
public void validate() {
validatePartitionBy();
validateFilter();
//......
if ( this.javascriptFile != null ) {
try {
this.scripting = new Scripting(this.javascriptFile);
} catch ( Exception e ) {
LOGGER.error("Error setting up javascript: ", e);
System.exit(1);
}
}
}
//......
}
- MaxwellConfig的validate方法在javascriptFile不为null的时候会创建Scripting,如果出现异常则执行System.exit(1)
小结
Scripting定义了processRowFunc、processHeartbeatFunc、processDDLFunc属性;其构造器接收filename参数,它创建ScriptEngineManager,然后获取名为nashorn的ScriptEngine,之后通过filename获取externJS,并执行engine.eval(externJS),之后通过getFunc方法初始化化processRowFunc、processHeartbeatFunc、processDDLFunc;其getFunc方法通过engine.get(fName)获取ScriptObjectMirror;其invoke方法针对HeartbeatRowMap执行processHeartbeatFunc.call,针对DDLMap执行processDDLFunc.call,针对RowMap执行processRowFunc.call
doc
来源:oschina
链接:https://my.oschina.net/go4it/blog/4273405