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本文主要研究一下canal的CanalEventFilter
CanalEventFilter
canal-1.1.4/filter/src/main/java/com/alibaba/otter/canal/filter/CanalEventFilter.java
public interface CanalEventFilter<T> {
boolean filter(T event) throws CanalFilterException;
}
- CanalEventFilter接口定义了filter方法
AviaterELFilter
canal-1.1.4/filter/src/main/java/com/alibaba/otter/canal/filter/aviater/AviaterELFilter.java
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);
}
}
- AviaterELFilter实现了CanalEventFilter接口,其构造器接收expression参数,其filter方法通过AviatorEvaluator.execute(expression, env)计算结果
AviaterSimpleFilter
canal-1.1.4/filter/src/main/java/com/alibaba/otter/canal/filter/aviater/AviaterSimpleFilter.java
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);
}
}
- AviaterSimpleFilter实现了CanalEventFilter接口;它定义了Expression属性,其值为AviatorEvaluator.compile(FILTER_EXPRESSION, true);其构造器接收filterExpression;其filter方法通过exp.execute(env)返回结果
AviaterRegexFilter
canal-1.1.4/filter/src/main/java/com/alibaba/otter/canal/filter/aviater/AviaterRegexFilter.java
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;
}
}
- AviaterRegexFilter实现了CanalEventFilter接口;它定义了Expression属性,其值为AviatorEvaluator.compile(FILTER_EXPRESSION, true);其构造器接收pattern参数,它会先对pattern进行sort以及修正;其filter方法通过exp.execute(env)返回结果
小结
CanalEventFilter接口定义了filter方法;它三个实现类分别是AviaterELFilter、AviaterSimpleFilter、AviaterRegexFilter
doc
来源:oschina
链接:https://my.oschina.net/go4it/blog/3228232