目录
背景
思路
实现
背景
前段时间的任务中，遇到了需要识别两个对象不同属性的场景，如果使用传统的一个个属性比对equals方法，会存在大量的重复工作，而且为对象新增了属性后，比对方法也需要同步修改，不方便维护，于是便打算构造一个通用的比对方法，需要支持对象嵌套,并支持过滤比对逻辑的策略，适用大部分比对场景
思路
一个java对象，他的属性是多样的，会有集合类型（如Collection，Map，Array），基本类型（如String,int,double,long等认为是最基本对象的比较），或者对象类型，本质上是一个树状的结构
怎么去遍历对象树
常用的方法就是递归，那怎么定义递归的终点？基于上面三种类型，定为基本类型的比对为递归的终点，对于集合类型，那就再对每一个元素进行比较，对于对象类型，遍历属性进行比较
为了达成通用目的，这里使用java反射实现，基于约定和性能考虑，只通过无参的getter方法获取属性进行比较，另外如何记录当前属性所在的路径？这里参考spel表达式，相对轻量直观
实现
首先定义递归过程记录的上下文信息
这里记录了根对象，当前处理的对象，以及反射获取的对象信息
protected static class CompareContext {
//对比结果
private List<CompareResult.CompareInfo> resCollect;
//当前遍历的对象信息,用于定位
private ArrayDeque<String> pathMessageStack;
protected Object rootSourceObj;
protected Object rootOtherObj;
protected Object sourceObj;
protected Object otherObj;
protected Object sourceInvokeVal;
protected Object otherInvokeVal;
//过滤耗费时间
private long filterCost;
private String checkCycle() {
Set<String> set = new LinkedHashSet<>();
//出现重复退出
while (set.add(pathMessageStack.removeLast())) {
}
String[] elements = new String[set.size()];
Iterator<String> iterator = set.iterator();
int index = 0;
while (iterator.hasNext()) {
elements[set.size() - 1 - index++] = iterator.next();
}
return getPath(elements);
}
protected String getPath(String[] elements) {
Object obj = this.rootSourceObj == null ? this.rootOtherObj : this.rootSourceObj;
String simpleName = obj.getClass().getSimpleName();
StringBuilder builder = new StringBuilder(simpleName);
if (elements == null) {
elements = this.pathMessageStack.toArray(new String[0]);
}
for (int i = elements.length - 1; i >= 0; i--) {
String cur = elements[i];
String value = cur.substring(2);
if (cur.startsWith(FIELD_SIGN)) {
builder.append(".").append(value);
} else {
builder.append("[").append(value).append("]");
}
}
return builder.toString();
}
}基于这个上下文，定义过滤接口，因为有些属性可能不用比对，如果命中过滤接口，则跳过
@FunctionalInterface
public interface MethodFilter {
boolean isSkipCompare(Method method, String methodKey, CompareUtil.CompareContext compareContext);
}
比对结果类，主要存放每个比对不通过属性的值及其路径信息
@Getter
@ToString
public class CompareResult {
protected boolean same;
protected Object source;
protected Object other;
protected List<CompareInfo> diffList;
//=====额外信息，可以不关注====
//整体对比耗时
private long totalCostMill;
//方法过滤耗时
protected long methodFilterCostMill;
protected void genCost(long start) {
this.totalCostMill = System.currentTimeMillis() - start;
}
@Getter
public static class CompareInfo {
protected Object sourceVal;
protected Object otherVal;
protected String path;
protected boolean isShow() {
if (sourceVal == null || otherVal == null) {
return true;
}
if (CompareUtil.getObjType(sourceVal) != Object.class) {
return true;
}
if (sourceVal instanceof Collection) {
return ((Collection<?>) sourceVal).size() != ((Collection<?>) otherVal).size();
}
if (sourceVal instanceof Map) {
return ((Map<?, ?>) sourceVal).size() != ((Map<?, ?>) otherVal).size();
}
if (sourceVal.getClass().isArray()) {
return ((Object[]) sourceVal).length != ((Object[]) otherVal).length;
}
return false;
}
@Override
public String toString() {
return String.format("path:%s,source:[%s],other:[%s]", path, sourceVal, otherVal);
}
}
public String getBaseObjDiffInfo() {
return getBaseObjDiffInfo("\n");
}
/**
* 过滤出为空的父对象或基本对象，原生的diffList会包含父对象，不方便查看
*
* @param seperator
* @return
*/
public String getBaseObjDiffInfo(String seperator) {
if (!same) {
StringBuilder builder = new StringBuilder();
diffList.stream().filter(CompareInfo::isShow).forEach(v -> builder.append(v).append(seperator));
return builder.toString();
}
return "";
}
}
随后定义入口方法
public static <T> CompareResult compareObjByGetter(T source, T other, MethodFilter... methodFilters) {
List<CompareResult.CompareInfo> diffList = new ArrayList<>();
CompareContext compareContext = new CompareContext();
compareContext.resCollect = diffList;
compareContext.pathMessageStack = new ArrayDeque<>(MAX_DEEP_SIZE);
compareContext.rootSourceObj = source;
compareContext.rootOtherObj = other;
long start = System.currentTimeMillis();
boolean res = compareObjByGetter(source, other, compareContext, methodFilters);
CompareResult compareResult = new CompareResult();
compareResult.genCost(start);
compareResult.diffList = diffList;
compareResult.same = res;
compareResult.other = other;
compareResult.source = source;
compareResult.methodFilterCostMill = compareContext.filterCost;
return compareResult;
}主流程方法，流程如下
- 校验
- 路径长度校验
- 类校验
- 递归终点，对于基本类型，直接走比对方法,并生成路径
- 对于复合类型，递归进行比对逻辑
- 对于对象类型，采用反射获取具体值，并通过方法过滤进行比较
- 首先判断是否有public的无参数getter方法
- 有的话采用调用该方法获取两边的值，设置上下文信息
- 过滤器过滤无需比对的字段
- 如果任一方为空，构造结果
- 对于集合类型的属性，需要进一步获取里面的元素进行递归处理
- 对于对象类型或基本类型，重复上述步骤
主流程代码如下
private static <T> boolean compareObjByGetter(T source, T other, CompareContext compareContext, MethodFilter... methodFilters) {
//对比路径太深或出现循环引用不支持
if (compareContext.pathMessageStack.size() > MAX_DEEP_SIZE) {
String path = compareContext.checkCycle();
if (!StringUtils.isEmpty(path)) {
//路径仅供参考，不一定准确
throw new IllegalStateException(String.format("reference cycle happen,please check your object,path:%s", path));
}
throw new IllegalStateException(String.format("compare path over max size:%s,please check your object", MAX_DEEP_SIZE));
}
if(source==other){
return true;
}
if (source == null || other == null) {
generateResult(source, other, compareContext);
return false;
}
if (!source.getClass().equals(other.getClass())) {
throw new IllegalArgumentException(String.format("not the same object,class source:%s,class other:%s,path:%s", source.getClass(), other.getClass(),compareContext.getPath(null)));
}
//基本类型不再对比getter方法
if (getObjType(source) != Object.class) {
boolean isSame = compareBaseObj(source, other);
if (!isSame) {
generateResult(source, other, compareContext);
}
return isSame;
}
//复合类型
if (isCollectionOrMapOrArray(source)) {
return dealWithCMA(source, other, compareContext, methodFilters);
}
//对象类型，遍历对应的方法
final boolean[] val = new boolean[]{true};
ReflectionUtils.doWithMethods(source.getClass(), new ReflectionUtils.MethodCallback() {
@Override
public void doWith(Method method) throws IllegalArgumentException, IllegalAccessException {
String name = method.getName();
if (method.getModifiers() == Modifier.PUBLIC && (name.startsWith("get") || name.startsWith("is"))) {
//有入参的getter不处理
if (method.getParameterTypes().length != 0) {
return;
}
String methodKey = method.getDeclaringClass().getName() + "#" + method.getName();
Object sourceInvokeVal = null;
Object otherInvokeVal = null;
try {
sourceInvokeVal = method.invoke(source);
otherInvokeVal = method.invoke(other);
} catch (Exception e) {
throw new RuntimeException(e);
}
compareContext.otherObj = other;
compareContext.otherInvokeVal = otherInvokeVal;
compareContext.sourceObj = source;
compareContext.sourceInvokeVal = sourceInvokeVal;
//过滤,methodFilter是||关系
long start = System.currentTimeMillis();
try {
for (MethodFilter methodFilter : methodFilters) {
if (methodFilter.isSkipCompare(method, methodKey, compareContext)) {
return;
}
}
} finally {
compareContext.filterCost += System.currentTimeMillis() - start;
}
if (sourceInvokeVal == null && otherInvokeVal == null) {
return;
}
compareContext.pathMessageStack.push(String.format("%s%s", FIELD_SIGN, ColumnSelector.getFieldName(method.getName(), method.getDeclaringClass().getName())));
if (sourceInvokeVal == null || otherInvokeVal == null) {
generateResult(sourceInvokeVal, otherInvokeVal, compareContext);
val[0] = false;
compareContext.pathMessageStack.pop();
return;
}
if (isCollectionOrMapOrArray(sourceInvokeVal)) {
val[0] &= dealWithCMA(sourceInvokeVal, otherInvokeVal, compareContext, methodFilters);
} else {
//对象类型 or 基本类型
val[0] &= compareObjByGetter(sourceInvokeVal, otherInvokeVal, compareContext, methodFilters);
}
compareContext.pathMessageStack.pop();
}
}
});
return val[0];
}对于集合类型的处理如下
主要根据各自的特性取出元素，再给到上面的主流程去执行
private static boolean dealWithCMA(Object sourceObj, Object otherObj, CompareContext compareContext, MethodFilter... methodFilters) {
if(sourceObj==otherObj){
return true;
}
boolean isDiff = true;
if (sourceObj instanceof Collection) {
Collection<?> sourceCollection = ((Collection<?>) sourceObj);
Collection<?> otherCollection = ((Collection<?>) otherObj);
//要求顺序,这里不做排序
if (sourceCollection.size() != otherCollection.size()) {
isDiff = false;
} else {
Iterator<?> sourceI = sourceCollection.iterator();
Iterator<?> otherI = otherCollection.iterator();
int index = 0;
while (sourceI.hasNext()) {
Object sourceElement = sourceI.next();
Object otherElement = otherI.next();
//下一层不匹配的值
compareContext.pathMessageStack.push(String.format("%s%s", COLLECTION_SIGN, index++));
isDiff &= compareObjByGetter(sourceElement, otherElement, compareContext, methodFilters);
compareContext.pathMessageStack.pop();
}
}
}
if (sourceObj.getClass().isArray()) {
Object[] sourceArray = (Object[]) sourceObj;
Object[] otherArray = (Object[]) otherObj;
if (sourceArray.length != otherArray.length) {
isDiff = false;
} else {
for (int i = 0; i < sourceArray.length; i++) {
Object sourceElement = sourceArray[i];
Object otherElement = otherArray[i];
compareContext.pathMessageStack.push(String.format("%s%s", ARRAY_SIGN, i));
isDiff &= compareObjByGetter(sourceElement, otherElement, compareContext, methodFilters);
compareContext.pathMessageStack.pop();
}
}
}
if (sourceObj instanceof Map) {
Map<?, ?> sourceMap = (Map) sourceObj;
Map<?, ?> otherMap = (Map) otherObj;
if (sourceMap.size() != otherMap.size()) {
isDiff = false;
} else {
HashSet<?> otherKeySet = new HashSet<>(otherMap.keySet());
for (Map.Entry<?, ?> entry : sourceMap.entrySet()) {
Object sourceKey = entry.getKey();
Object otherVal = otherMap.get(sourceKey);
otherKeySet.remove(sourceKey);
compareContext.pathMessageStack.push(String.format("%s%s", KEY_SIGN, sourceKey));
isDiff &= compareObjByGetter(entry.getValue(), otherVal, compareContext, methodFilters);
compareContext.pathMessageStack.pop();
}
if (!otherKeySet.isEmpty()) {
for (Object otherKey : otherKeySet) {
compareContext.pathMessageStack.push(String.format("%s%s", KEY_SIGN, otherKey));
isDiff &= compareObjByGetter(null, otherMap.get(otherKey), compareContext, methodFilters);
compareContext.pathMessageStack.pop();
}
}
}
}
if (!isDiff) {
generateResult(sourceObj, otherObj, compareContext);
}
return isDiff;
}对于基本对象判断，如果返回object类型需要进一步解析判断，后续如果有其他基本对象，比如业务自定义的基本对象也可以往里面加，或者再进行优化，通过本地线程的方式动态指定基本对象类型
/**
* 后续比对有其他基本类型可以往里加
* @param obj
* @return
*/
protected static Class<?> getObjType(Object obj) {
if (obj instanceof Integer) {
return Integer.class;
} else if (obj instanceof String) {
return String.class;
} else if (obj instanceof BigDecimal) {
return BigDecimal.class;
} else if (obj instanceof Long) {
return Long.class;
} else if (obj instanceof Enum) {
return Enum.class;
} else if (obj instanceof Double) {
return Double.class;
} else if (obj instanceof Boolean) {
return Boolean.class;
}
return Object.class;
}对于基本类型的比较方法
private static <T> boolean compareBaseObj(T obj, T other) {
//同一个对象直接通过
if(obj==other){
return true;
}
//数字类型
if (obj instanceof Number && obj instanceof Comparable) {
return ((Comparable<T>) obj).compareTo(other) == 0;
}
//其他类型
return Objects.equals(obj, other);
}
效果
Java对象比对功能实现大概如此，来看看效果
定义了比对对象
@Getter
public static class ComposeObj {
private String id;
private Object[] arrays;
private List<Object> list;
private Map<String, Object> map;
private ComposeObj son;
private int idLength;
public ComposeObj(String id) {
this.id = id;
this.idLength = id.length();
}
}测试代码
ComposeObj sourceObj = new ComposeObj("source");
ComposeObj arrayObj = new ComposeObj("A1");
sourceObj.arrays = new Object[]{arrayObj, new ComposeObj("A22")};
sourceObj.list = Arrays.asList(new ComposeObj("C1"), new ComposeObj("C11"));
Map<String, Object> map = new HashMap<>();
map.put("test", "test");
map.put("test2", "test2");
sourceObj.map = map;
ComposeObj otherObj = new ComposeObj("other");
ComposeObj arrayObj2 = new ComposeObj("A2");
otherObj.arrays = new Object[]{arrayObj2, new ComposeObj("A22")};
otherObj.list = Arrays.asList(new ComposeObj("C2"), new ComposeObj("C11"));
Map<String, Object> map2 = new HashMap<>();
map2.put("test", "test2");
map2.put("test2", "test22");
otherObj.map = map2;测试方法
CompareResult compareResult = CompareUtil.compareObjByGetter(sourceObj, otherObj);
assert checkPath(compareResult);
assert compareResult.getDiffList().size() == 9;
log.info(compareResult.getBaseObjDiffInfo());结果
默认的支持的表达式过滤器如下
/**
* 通过简单的表达式
* "*abc|xxx" ->标识以abc结尾或xxx的属性忽略，不做比对,*代表通配符
*/
public class RegexFieldFilter implements MethodFilter {
private static final Cache<String, Pattern> REGEX_MAP = CacheBuilder.newBuilder()
.softValues().maximumSize(2048).build();
private final List<String> rules;
private static final String WILDCARD = "*";
//是否缓存结果，如果调用次数较多（比如属性为list，且实际场景数量较多）可以用启用
private boolean cacheResult = false;
//方法key
private Cache<String, Boolean> resultMap;
private final Set<String> equalsField = new HashSet<>();
private final Map<String, String> prefixFieldMap = new HashMap<>();
private final Map<String, String> suffixFieldMap = new HashMap<>();
private RegexFieldFilter(String regex, boolean cacheResult) {
this.cacheResult = cacheResult;
rules = Splitter.on("|").splitToList(regex);
for (String rule : rules) {
//普通比对
if (!rule.contains(WILDCARD)) {
equalsField.add(rule);
}
//首尾通配符特殊逻辑
if (onlyOneWildcard(rule)) {
if (rule.startsWith(WILDCARD)) {
suffixFieldMap.put(rule, rule.substring(1));
}
if (rule.endsWith(WILDCARD)) {
prefixFieldMap.put(rule, rule.substring(0, rule.length() - 1));
}
}
}
if (cacheResult) {
resultMap = CacheBuilder.newBuilder().softValues().maximumSize(1024).build();
}
}
public static RegexFieldFilter of(String regex, boolean cacheResult) {
return new RegexFieldFilter(regex, cacheResult);
}
public static RegexFieldFilter of(String regex) {
return of(regex, false);
}
private boolean canSkip(String rule, String fieldName) {
if (rule.contains(WILDCARD)) {
if (suffixFieldMap.containsKey(rule)) {
return fieldName.endsWith(suffixFieldMap.get(rule));
}
if (prefixFieldMap.containsKey(rule)) {
return fieldName.startsWith(prefixFieldMap.get(rule));
}
//在中间或多个通配符
String replace = StringUtils.replace(rule, WILDCARD, ".*");
Pattern pattern = REGEX_MAP.asMap().computeIfAbsent(replace, Pattern::compile);
return pattern.matcher(fieldName).matches();
}
return equalsField.contains(fieldName);
}
private boolean onlyOneWildcard(String rule) {
if (!rule.contains(WILDCARD)) {
return false;
}
return rule.indexOf(WILDCARD, rule.indexOf(WILDCARD) + 1) == -1;
}
@Override
public boolean isSkipCompare(Method method, String methodKey, CompareUtil.CompareContext context) {
return cacheResult ? resultMap.asMap().computeIfAbsent(methodKey, s -> judgeSkip(method)) : judgeSkip(method);
}
private boolean judgeSkip(Method method) {
if (!CollectionUtils.isEmpty(rules)) {
String name = method.getName();
String fieldName = CompareUtil.getFieldName(name, method.getDeclaringClass().getCanonicalName());
for (String rule : rules) {
if (canSkip(rule, fieldName)) {
return true;
}
}
}
return false;
}
}测试代码如下，定义这个过滤会把属性名为arrays,带有'l',或者ma开头的属性都过滤掉，不参与比对逻辑
boolean cacheResult = false;
RegexFieldFilter of = RegexFieldFilter.of("arrays|*l*|ma*", cacheResult);
CompareResult compareResult = CompareUtil.compareObjByGetter(source, other, of);
assert checkPath(compareResult);
assert compareResult.getDiffList().size() == 15;ComopareUtil完整代码
https://github.com/97lele/redis-aux/tree/dev/common/src/main/java/com/xl/redisaux/common/utils/compare
