add COLA rule engine

cola-components/cola-component-ruleengine/README.md

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+## 介绍
+这是COLA规则引擎
+
+## 使用
+hello world 案例：
+```java
+        RuleEngine ruleEngine = new DefaultRuleEngine();
+        Rule rule = new RuleBuilder()
+                .name("hello world rule")
+                .description("always say hello world")
+                .priority(1)
+                .when(facts -> true)
+                .then(facts -> System.out.println("hello world"))
+                .build();
+        Rules rules = new Rules();
+        rules.register(rule);
+
+        ruleEngine.fire(rules, null);
+```
+

cola-components/cola-component-ruleengine/gitignore.txt

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+target/
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+out/
+
+### NetBeans ###
+nbproject/private/
+build/
+nbbuild/
+dist/
+nbdist/
+bin/
+doc/
+.DS_Store

cola-components/cola-component-ruleengine/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.alibaba.cola</groupId>
+        <artifactId>cola-components-parent</artifactId>
+        <version>4.4.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>cola-component-ruleengine</artifactId>
+    <packaging>jar</packaging>
+    <name>${project.artifactId}:${project.version}</name>
+    <description>${project.artifactId}</description>
+    <url>https://github.com/alibaba/COLA</url>
+
+    <licenses>
+        <license>
+            <name>GNU Lesser General Public License v2.1</name>
+            <url>https://github.com/alibaba/COLA/blob/master/LICENSE</url>
+            <distribution>repo</distribution>
+        </license>
+    </licenses>
+    <scm>
+        <connection>scm:git:https://github.com/alibaba/COLA.git</connection>
+        <developerConnection>scm:git:https://github.com/alibaba/COLA.git</developerConnection>
+        <url>https://github.com/alibaba/COLA</url>
+    </scm>
+    <issueManagement>
+        <url>https://github.com/alibaba/COLA/issues</url>
+        <system>GitHub Issues</system>
+    </issueManagement>
+    <developers>
+        <developer>
+            <id>significantfrank</id>
+            <name>Frank Zhang</name>
+            <email>25216348(at)qq.com</email>
+            <roles>
+                <role>Developer</role>
+                <role>Architect</role>
+            </roles>
+            <timezone>+8</timezone>
+            <url>https://github.com/significantfrank</url>
+        </developer>
+        <developer>
+            <id>oldratlee</id>
+            <name>Jerry Lee</name>
+            <email>oldratlee(at)gmail.com</email>
+            <roles>
+                <role>Developer</role>
+                <role>CI/SCM Engineer</role>
+            </roles>
+            <timezone>+8</timezone>
+            <url>https://github.com/oldratlee</url>
+        </developer>
+    </developers>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+        </dependency>
+
+        <!-- test dependencies -->
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-simple</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>

cola-components/cola-component-ruleengine/src/main/java/com/alibaba/cola/ruleengine/api/Action.java

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+package com.alibaba.cola.ruleengine.api;
+
+@FunctionalInterface
+public interface Action {
+    void execute(Facts facts);
+}
+

cola-components/cola-component-ruleengine/src/main/java/com/alibaba/cola/ruleengine/api/Condition.java

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+package com.alibaba.cola.ruleengine.api;
+
+import java.util.Objects;
+
+@FunctionalInterface
+public interface Condition {
+
+    boolean evaluate(Facts facts);
+
+    //谓词and逻辑，参考Predicate
+    default Condition and(Condition other) {
+        Objects.requireNonNull(other);
+        return (facts) -> {
+            return this.evaluate(facts) && other.evaluate(facts);
+        };
+    }
+
+    //谓词or逻辑，参考Predicate
+    default Condition or(Condition other) {
+        Objects.requireNonNull(other);
+        return (facts) -> {
+            return this.evaluate(facts) || other.evaluate(facts);
+        };
+    }
+
+    /**
+     * A NoOp {@link Condition} that always returns false.
+     */
+    Condition FALSE = facts -> false;
+
+    /**
+     * A NoOp {@link Condition} that always returns true.
+     */
+    Condition TRUE = facts -> true;
+}
+

cola-components/cola-component-ruleengine/src/main/java/com/alibaba/cola/ruleengine/api/Fact.java

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+package com.alibaba.cola.ruleengine.api;
+
+import java.util.Objects;
+
+public class Fact<T> {
+
+    private final String name;
+    private final T value;
+
+    /**
+     * Create a new fact.
+     * @param name of the fact
+     * @param value of the fact
+     */
+    public Fact(String name, T value) {
+        Objects.requireNonNull(name, "name must not be null");
+        Objects.requireNonNull(value, "value must not be null");
+        this.name = name;
+        this.value = value;
+    }
+
+    /**
+     * Get the fact name.
+     * @return fact name
+     */
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * Get the fact value.
+     * @return fact value
+     */
+    public T getValue() {
+        return value;
+    }
+
+    @Override
+    public String toString() {
+        return "Fact{" +
+                "name='" + name + '\'' +
+                ", value=" + value +
+                '}';
+    }
+
+    /*
+     * The Facts API represents a namespace for facts where each fact has a unique name.
+     * Hence, equals/hashcode are deliberately calculated only on the fact name.
+     */
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Fact<?> fact = (Fact<?>) o;
+        return name.equals(fact.name);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(name);
+    }
+}

cola-components/cola-component-ruleengine/src/main/java/com/alibaba/cola/ruleengine/api/Facts.java

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+package com.alibaba.cola.ruleengine.api;
+
+import java.util.*;
+
+public class Facts implements Iterable<Fact<?>> {
+
+    private final Set<Fact<?>> facts = new HashSet<>();
+
+    /**
+     * Add a fact, replacing any fact with the same name.
+     *
+     * @param name of the fact to add, must not be null
+     * @param value of the fact to add, must not be null
+     */
+    public <T> void put(String name, T value) {
+        Objects.requireNonNull(name, "fact name must not be null");
+        Objects.requireNonNull(value, "fact value must not be null");
+        Fact<?> retrievedFact = getFact(name);
+        if (retrievedFact != null) {
+            remove(retrievedFact);
+        }
+        add(new Fact<>(name, value));
+    }
+
+    /**
+     * Add a fact, replacing any fact with the same name.
+     *
+     * @param fact to add, must not be null
+     */
+    public <T> void add(Fact<T> fact) {
+        Objects.requireNonNull(fact, "fact must not be null");
+        Fact<?> retrievedFact = getFact(fact.getName());
+        if (retrievedFact != null) {
+            remove(retrievedFact);
+        }
+        facts.add(fact);
+    }
+
+    /**
+     * Remove a fact by name.
+     *
+     * @param factName name of the fact to remove, must not be null
+     */
+    public void remove(String factName) {
+        Objects.requireNonNull(factName, "fact name must not be null");
+        Fact<?> fact = getFact(factName);
+        if (fact != null) {
+            remove(fact);
+        }
+    }
+
+    /**
+     * Remove a fact.
+     *
+     * @param fact to remove, must not be null
+     */
+    public <T> void remove(Fact<T> fact) {
+        Objects.requireNonNull(fact, "fact must not be null");
+        facts.remove(fact);
+    }
+
+    /**
+     * Get the value of a fact by its name. This is a convenience method provided
+     * as a short version of {@code getFact(factName).getValue()}.
+     *
+     * @param factName name of the fact, must not be null
+     * @param <T> type of the fact's value
+     * @return the value of the fact having the given name, or null if there is
+     * no fact with the given name
+     */
+    @SuppressWarnings("unchecked")
+    public <T> T get(String factName) {
+        Objects.requireNonNull(factName, "fact name must not be null");
+        Fact<?> fact = getFact(factName);
+        if (fact != null) {
+            return (T) fact.getValue();
+        }
+        return null;
+    }
+
+    /**
+     * Get a fact by name.
+     *
+     * @param factName name of the fact, must not be null
+     * @return the fact having the given name, or null if there is no fact with the given name
+     */
+    public Fact<?> getFact(String factName) {
+        Objects.requireNonNull(factName, "fact name must not be null");
+        return facts.stream()
+                .filter(fact -> fact.getName().equals(factName))
+                .findFirst()
+                .orElse(null);
+    }
+
+    /**
+     * Return a copy of the facts as a map. It is not intended to manipulate
+     * facts outside of the rules engine (aka other than manipulating them through rules).
+     *
+     * @return a copy of the current facts as a {@link HashMap}
+     */
+    public Map<String, Object> asMap() {
+        Map<String, Object> map = new HashMap<>();
+        for (Fact<?> fact : facts) {
+            map.put(fact.getName(), fact.getValue());
+        }
+        return map;
+    }
+
+    /**
+     * Return an iterator on the set of facts. It is not intended to remove
+     * facts using this iterator outside of the rules engine (aka other than doing it through rules)
+     *
+     * @return an iterator on the set of facts
+     */
+    @Override
+    public Iterator<Fact<?>> iterator() {
+        return facts.iterator();
+    }
+
+    /**
+     * Clear facts.
+     */
+    public void clear() {
+        facts.clear();
+    }
+
+    @Override
+    public String toString() {
+        Iterator<Fact<?>> iterator = facts.iterator();
+        StringBuilder stringBuilder = new StringBuilder("[");
+        while (iterator.hasNext()) {
+            stringBuilder.append(iterator.next().toString());
+            if (iterator.hasNext()) {
+                stringBuilder.append(",");
+            }
+        }
+        stringBuilder.append("]");
+        return stringBuilder.toString();
+    }
+}