提要：
使用表达式求值和groovy脚本来生成flink cep Pattern。减少代码量，一份代码可通过传script脚本的方式生成不同的pattern。
1.source

 SingleOutputStreamOperator<MetricEvent> metricEvent = dataStreamSource
                .flatMap(new ParseMetricEventFunction()).returns(MetricEvent.class);

2.pattern

Pattern p1 = ScriptEngine.getPattern(

                "  import org.apache.flink.cep.nfa.aftermatch.AfterMatchSkipStrategy\n" +
                        "import org.apache.flink.cep.pattern.Pattern\n" +
                        "import test.cep.function.AviatorCondition \n" +

                        "where1 = new AviatorCondition(" +
                        "   \"getT(tags,\\\"cluster_name\\\")==\\\"x\\\"&&getF(fields,\\\"load5\\\")>15 \"" +
                        "        )\n" +

                        "def get(){ " +
                        "      return Pattern.begin(\"start\", AfterMatchSkipStrategy.noSkip())\n" +
                        "        .where(where1)" +
                        "}",
                "get");

3.result

  PatternStream pStream2 = CEP.pattern(metricEvent.keyBy(metricEvent1 -> metricEvent1.getName() + Joiner.on(",").join(metricEvent1.getTags().values())), p);
        SingleOutputStreamOperator filter2 = pStream2.select(new PatternSelectFunction<MetricEvent, String>() {
            @Override
            public String select(Map<String, List<MetricEvent>> pattern) throws Exception {
                return "-----------------------------" + pattern.toString();
            }
        });

        filter2.print();

        StateBackend memory = new MemoryStateBackend(10 * 5 * 1024 * 1024, true);
        env.setStateBackend(memory);
        env.execute("----flink cep alert ----");

4.model

@Data
public class MetricEvent {

    private String name;

    private long timestamp;

    private Map<String, Object> fields = new HashMap<>();

    private Map<String, String> tags = new HashMap<>();
}

5.ScriptEngine

import org.apache.flink.cep.pattern.Pattern;

import javax.script.Bindings;
import javax.script.Invocable;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import java.util.Date;

public class ScriptEngine {

   public static Pattern getPattern(String text,String name) throws ScriptException, NoSuchMethodException {
       ScriptEngineManager factory = new ScriptEngineManager();
       javax.script.ScriptEngine engine =  factory.getEngineByName("groovy");
       System.out.println(engine.toString());
       assert engine != null;
       engine.eval(text);
       Pattern pattern = (Pattern)((Invocable)engine).invokeFunction(name);
       return pattern;
   }
}

6.表达式相关
GetTagMapFunction

public class GetTagMapFunction extends AbstractFunction {
    @Override
    public String getName() {
        return "getF";
    }
    @Override
    public AviatorDouble call(Map<String, Object> env, AviatorObject args1, AviatorObject args2) {
        Map<String, Object> map = (Map<String, Object>) FunctionUtils.getJavaObject(args1, env);
        String field = FunctionUtils.getStringValue(args2, env);
        return new AviatorDouble((Double) map.get(field));
    }
}

GetFieldMapFunction

public class GetFieldMapFunction extends AbstractFunction {
    @Override
    public String getName() {
        return "getT";
    }

    @Override
    public AviatorString call(Map<String, Object> env, AviatorObject args1, AviatorObject args2) {
        Map<String, String> map = (Map<String, String>) FunctionUtils.getJavaObject(args1, env);
        String field = FunctionUtils.getStringValue(args2, env);
        return new AviatorString(map.get(field));
    }

}

7.表达式Condition,注册表达式

public class AviatorCondition extends SimpleCondition<MetricEvent> implements Serializable {
    private static Logger logger = LoggerFactory.getLogger(AviatorCondition.class);
    private String script;
    static {
        AviatorEvaluator.addFunction(new GetFieldMapFunction());
        AviatorEvaluator.addFunction(new GetTagMapFunction());
    }
    public AviatorCondition(String script) {
        this.script = script;
    }
    @Override
    public boolean filter(MetricEvent event) throws Exception {
        Map<String, Object> env = new HashMap<String, Object>();
        env.put("event", event);
        env.put("fields", event.getFields());
        env.put("tags", event.getTags());
        Boolean result = false;
        try {
            result = (Boolean) AviatorEvaluator.execute(script, env);
        } catch (Exception e) {
            logger.error("execute script with event error,script:{},event:{},error;{}", script, event, e);
        }
        return result;
    }
}

8.依赖

 <dependency>
            <groupId>com.googlecode.aviator</groupId>
            <artifactId>aviator</artifactId>
            <version>2.3.3</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.groovy</groupId>
            <artifactId>groovy</artifactId>
            <version>2.4.7</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.groovy</groupId>
            <artifactId>groovy-jsr223</artifactId>
            <version>2.4.7</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.groovy</groupId>
            <artifactId>groovy</artifactId>
            <version>2.4.7</version>
        </dependency>
       

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.51</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-cep-scala_2.11</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.34</version>
        </dependency>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>26.0-jre</version>
        </dependency>