聊聊canal的CanalEventFilter

public interface CanalEventFilter<T> {
​
    boolean filter(T event) throws CanalFilterException;
}

public class AviaterELFilter implements CanalEventFilter<CanalEntry.Entry> {
​
    public static final String ROOT_KEY = "entry";
    private String             expression;
​
    public AviaterELFilter(String expression){
        this.expression = expression;
    }
​
    public boolean filter(CanalEntry.Entry entry) throws CanalFilterException {
        if (StringUtils.isEmpty(expression)) {
            return true;
        }
​
        Map<String, Object> env = new HashMap<String, Object>();
        env.put(ROOT_KEY, entry);
        return (Boolean) AviatorEvaluator.execute(expression, env);
    }
​
}

public class AviaterSimpleFilter implements CanalEventFilter<String> {
​
    private static final String SPLIT             = ",";
​
    private static final String FILTER_EXPRESSION = "include(list,target)";
​
    private final Expression    exp               = AviatorEvaluator.compile(FILTER_EXPRESSION, true);
​
    private final List<String>  list;
​
    public AviaterSimpleFilter(String filterExpression){
        if (StringUtils.isEmpty(filterExpression)) {
            list = new ArrayList<String>();
        } else {
            String[] ss = filterExpression.toLowerCase().split(SPLIT);
            list = Arrays.asList(ss);
        }
    }
​
    public boolean filter(String filtered) throws CanalFilterException {
        if (list.isEmpty()) {
            return true;
        }
        if (StringUtils.isEmpty(filtered)) {
            return true;
        }
        Map<String, Object> env = new HashMap<String, Object>();
        env.put("list", list);
        env.put("target", filtered.toLowerCase());
        return (Boolean) exp.execute(env);
    }
​
}

public class AviaterRegexFilter implements CanalEventFilter<String> {
​
    private static final String             SPLIT             = ",";
    private static final String             PATTERN_SPLIT     = "|";
    private static final String             FILTER_EXPRESSION = "regex(pattern,target)";
    private static final RegexFunction      regexFunction     = new RegexFunction();
    private final Expression                exp               = AviatorEvaluator.compile(FILTER_EXPRESSION, true);
    static {
        AviatorEvaluator.addFunction(regexFunction);
    }
​
    private static final Comparator<String> COMPARATOR        = new StringComparator();
​
    final private String                    pattern;
    final private boolean                   defaultEmptyValue;
​
    public AviaterRegexFilter(String pattern){
        this(pattern, true);
    }
​
    public AviaterRegexFilter(String pattern, boolean defaultEmptyValue){
        this.defaultEmptyValue = defaultEmptyValue;
        List<String> list = null;
        if (StringUtils.isEmpty(pattern)) {
            list = new ArrayList<String>();
        } else {
            String[] ss = StringUtils.split(pattern, SPLIT);
            list = Arrays.asList(ss);
        }
​
        // 对pattern按照从长到短的排序
        // 因为 foo|foot 匹配 foot 会出错，原因是 foot 匹配了 foo 之后，会返回 foo，但是 foo 的长度和 foot
        // 的长度不一样
        Collections.sort(list, COMPARATOR);
        // 对pattern进行头尾完全匹配
        list = completionPattern(list);
        this.pattern = StringUtils.join(list, PATTERN_SPLIT);
    }
​
    public boolean filter(String filtered) throws CanalFilterException {
        if (StringUtils.isEmpty(pattern)) {
            return defaultEmptyValue;
        }
​
        if (StringUtils.isEmpty(filtered)) {
            return defaultEmptyValue;
        }
​
        Map<String, Object> env = new HashMap<String, Object>();
        env.put("pattern", pattern);
        env.put("target", filtered.toLowerCase());
        return (Boolean) exp.execute(env);
    }
​
    //......
​
    @Override
    public String toString() {
        return pattern;
    }
​
}