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本文主要研究一下PowerJob的Evaluator
Evaluator
tech/powerjob/server/core/evaluator/Evaluator.java
代码语言：javascript复制public interface Evaluator {
/**
* 使用给定输入计算表达式
*
* @param expression 可执行的表达式
* @param input 输入
* @return 计算结果
*/
Object evaluate(String expression, Object input);
}Evaluator接口定义了evaluate方法，它有expression和input两个参数，返回计算结果
GroovyEvaluator
tech/powerjob/server/core/evaluator/GroovyEvaluator.java
代码语言：javascript复制@Slf4j
@Component
public class GroovyEvaluator implements Evaluator {
private static final ScriptEngine ENGINE = new ScriptEngineManager().getEngineByName("groovy");
@Override
@SneakyThrows
public Object evaluate(String expression, Object input) {
Bindings bindings = ENGINE.createBindings();
bindings.put("context", input);
return ENGINE.eval(expression, bindings);
}
}GroovyEvaluator实现了Evaluator，它内置了一个groovy的ScriptEngine，其evaluate方法先创建bindings，然后传入参数，最后通过ENGINE.eval(expression, bindings)计算结果
DecisionNodeHandler
tech/powerjob/server/core/workflow/hanlder/impl/DecisionNodeHandler.java
代码语言：javascript复制@Slf4j
@Component
public class DecisionNodeHandler implements ControlNodeHandler {
private final GroovyEvaluator groovyEvaluator = new GroovyEvaluator();
/**
* 处理判断节点
* 1. 执行脚本
* 2. 根据返回值 disable 掉相应的边以及节点
*/
@Override
public void handle(PEWorkflowDAG.Node node, PEWorkflowDAG dag, WorkflowInstanceInfoDO wfInstanceInfo) {
String script = node.getNodeParams();
if (StringUtils.isBlank(script)) {
log.error("[Workflow-{}|{}]decision node's param is blank! nodeId:{}", wfInstanceInfo.getWorkflowId(), wfInstanceInfo.getWfInstanceId(), node.getNodeId());
throw new PowerJobException("decision node's param is blank!");
}
// wfContext must be a map
HashMap<String, String> wfContext = JSON.parseObject(wfInstanceInfo.getWfContext(), new TypeReference<HashMap<String, String>>() {
});
Object result;
try {
result = groovyEvaluator.evaluate(script, wfContext);
} catch (Exception e) {
log.error("[Workflow-{}|{}]failed to evaluate decision node,nodeId:{}", wfInstanceInfo.getWorkflowId(), wfInstanceInfo.getWfInstanceId(), node.getNodeId(), e);
throw new PowerJobException("can't evaluate decision node!");
}
boolean finalRes;
if (result instanceof Boolean) {
finalRes = ((Boolean) result);
} else if (result instanceof Number) {
finalRes = ((Number) result).doubleValue() > 0;
} else {
log.error("[Workflow-{}|{}]decision node's return value is illegal,nodeId:{},result:{}", wfInstanceInfo.getWorkflowId(), wfInstanceInfo.getWfInstanceId(), node.getNodeId(), JsonUtils.toJSONString(result));
throw new PowerJobException("decision node's return value is illegal!");
}
handleDag(finalRes, node, dag);
}
//......
} DecisionNodeHandler实例化了groovyEvaluator，其handle方法通过groovyEvaluator.evaluate(script, wfContext)来计算node的结果
小结
PowerJob的Evaluator接口定义了evaluate方法，它有expression和input两个参数，返回计算结果；GroovyEvaluator实现了Evaluator，它内置了一个groovy的ScriptEngine，其evaluate方法先创建bindings，然后传入参数，最后通过ENGINE.eval(expression, bindings)计算结果。
