add MapJoiner

hutool-core/src/main/java/cn/hutool/core/collection/iter/IterUtil.java

@@ -183,7 +183,7 @@ public class IterUtil {
 	/**
 	 * 获取指定Bean列表中某个字段，生成新的列表
 	 *
-	 * @param <R> 返回元素类型
+	 * @param <R>       返回元素类型
 	 * @param <V>       对象类型
 	 * @param iterable  对象列表
 	 * @param fieldName 字段名（会通过反射获取其值）
@@ -197,7 +197,7 @@ public class IterUtil {
 	/**
 	 * 获取指定Bean列表中某个字段，生成新的列表
 	 *
-	 * @param <R> 返回元素类型
+	 * @param <R>       返回元素类型
 	 * @param <V>       对象类型
 	 * @param iter      对象列表
 	 * @param fieldName 字段名（会通过反射获取其值）
@@ -211,7 +211,7 @@ public class IterUtil {
 			V value;
 			while (iter.hasNext()) {
 				value = iter.next();
-				result.add((R)FieldUtil.getFieldValue(value, fieldName));
+				result.add((R) FieldUtil.getFieldValue(value, fieldName));
 			}
 		}
 		return result;
@@ -460,6 +460,7 @@ public class IterUtil {
 	 * @param index    位置
 	 * @param <E>      元素类型
 	 * @return 元素，找不到元素返回{@code null}
+	 * @throws IndexOutOfBoundsException index < 0时报错
 	 * @since 5.8.0
 	 */
 	public static <E> E get(final Iterator<E> iterator, int index) throws IndexOutOfBoundsException {

hutool-core/src/main/java/cn/hutool/core/map/MapJoiner.java

@@ -0,0 +1,109 @@
+package cn.hutool.core.map;
+
+import cn.hutool.core.text.StrJoiner;
+import cn.hutool.core.text.StrUtil;
+import cn.hutool.core.util.ArrayUtil;
+
+import java.util.Iterator;
+import java.util.Map;
+import java.util.function.Predicate;
+
+/**
+ * Map拼接器，可以拼接包括Map、Entry列表等。
+ *
+ * @author looly
+ */
+public class MapJoiner {
+
+	private final StrJoiner joiner;
+	private final String keyValueSeparator;
+
+	/**
+	 * 构建一个MapJoiner
+	 *
+	 * @param separator         entry之间的连接符
+	 * @param keyValueSeparator kv之间的连接符
+	 * @return MapJoiner
+	 */
+	public static MapJoiner of(final String separator, final String keyValueSeparator) {
+		return of(StrJoiner.of(separator), keyValueSeparator);
+	}
+
+	/**
+	 * 构建一个MapJoiner
+	 *
+	 * @param joiner            entry之间的Joiner
+	 * @param keyValueSeparator kv之间的连接符
+	 * @return MapJoiner
+	 */
+	public static MapJoiner of(final StrJoiner joiner, final String keyValueSeparator) {
+		return new MapJoiner(joiner, keyValueSeparator);
+	}
+
+	/**
+	 * 构造
+	 *
+	 * @param joiner            entry之间的Joiner
+	 * @param keyValueSeparator kv之间的连接符
+	 */
+	public MapJoiner(final StrJoiner joiner, final String keyValueSeparator) {
+		this.joiner = joiner;
+		this.keyValueSeparator = keyValueSeparator;
+	}
+
+	/**
+	 * 追加Map
+	 *
+	 * @param <K>       键类型
+	 * @param <V>       值类型
+	 * @param map       Map
+	 * @param predicate Map过滤器
+	 * @return this
+	 */
+	public <K, V> MapJoiner append(final Map<K, V> map, final Predicate<Map.Entry<K, V>> predicate) {
+		return append(map.entrySet().iterator(), predicate);
+	}
+
+	/**
+	 * 追加Entry列表
+	 *
+	 * @param <K>       键类型
+	 * @param <V>       值类型
+	 * @param parts     Entry列表
+	 * @param predicate Map过滤器
+	 * @return this
+	 */
+	public <K, V> MapJoiner append(final Iterator<? extends Map.Entry<K, V>> parts, final Predicate<Map.Entry<K, V>> predicate) {
+		if (null == parts) {
+			return this;
+		}
+
+		Map.Entry<K, V> entry;
+		while (parts.hasNext()) {
+			entry = parts.next();
+			if (null == predicate || predicate.test(entry)) {
+				joiner.append(StrJoiner.of(this.keyValueSeparator).append(entry.getKey()).append(entry.getValue()));
+			}
+		}
+
+		return this;
+	}
+
+	/**
+	 * 追加其他字符串，其他字符串简单拼接
+	 *
+	 * @param params 字符串列表
+	 * @return this
+	 */
+	public MapJoiner append(final String... params) {
+		if(ArrayUtil.isNotEmpty(params)){
+			joiner.append(StrUtil.concat(false, params));
+		}
+		return this;
+	}
+
+	@Override
+	public String toString() {
+		return joiner.toString();
+	}
+}

hutool-core/src/main/java/cn/hutool/core/map/MapUtil.java

@@ -4,7 +4,6 @@ import cn.hutool.core.collection.CollUtil;
 import cn.hutool.core.collection.ListUtil;
 import cn.hutool.core.collection.iter.ArrayIter;
 import cn.hutool.core.collection.iter.IterUtil;
-import cn.hutool.core.convert.Convert;
 import cn.hutool.core.exceptions.UtilException;
 import cn.hutool.core.reflect.ConstructorUtil;
 import cn.hutool.core.text.StrUtil;
@@ -605,28 +604,30 @@ public class MapUtil extends MapGetUtil {
 	 * @return 连接后的字符串，map和otherParams为空返回""
 	 * @since 3.1.1
 	 */
-	public static <K, V> String join(final Map<K, V> map, final String separator, final String keyValueSeparator, final boolean isIgnoreNull, final String... otherParams) {
+	public static <K, V> String join(final Map<K, V> map, final String separator, final String keyValueSeparator,
-		final StringBuilder strBuilder = StrUtil.builder();
+									 final boolean isIgnoreNull, final String... otherParams) {
-		boolean isFirst = true;
+		return join(map, separator, keyValueSeparator, (entry) -> false == isIgnoreNull || entry.getKey() != null && entry.getValue() != null, otherParams);
-		if (isNotEmpty(map)) {
+	}
-			for (final Entry<K, V> entry : map.entrySet()) {
+
-				if (false == isIgnoreNull || entry.getKey() != null && entry.getValue() != null) {
+	/**
-					if (isFirst) {
+	 * 将map转成字符串
-						isFirst = false;
+	 *
-					} else {
+	 * @param <K>               键类型
-						strBuilder.append(separator);
+	 * @param <V>               值类型
-					}
+	 * @param map               Map，为空返回otherParams拼接
-					strBuilder.append(Convert.toStr(entry.getKey())).append(keyValueSeparator).append(Convert.toStr(entry.getValue()));
+	 * @param separator         entry之间的连接符
-				}
+	 * @param keyValueSeparator kv之间的连接符
-			}
+	 * @param predicate         键值对过滤
-		}
+	 * @param otherParams       其它附加参数字符串（例如密钥）
-		// 补充其它字符串到末尾，默认无分隔符
+	 * @return 连接后的字符串，map和otherParams为空返回""
-		if (ArrayUtil.isNotEmpty(otherParams)) {
+	 * @since 3.1.1
-			for (final String otherParam : otherParams) {
+	 */
-				strBuilder.append(otherParam);
+	public static <K, V> String join(final Map<K, V> map, final String separator, final String keyValueSeparator,
-			}
+									 final Predicate<Entry<K, V>> predicate, final String... otherParams) {
-		}
+		return MapJoiner.of(separator, keyValueSeparator)
-		return strBuilder.toString();
+				.append(map, predicate)
+				.append(otherParams)
+				.toString();
 	}
 
 	// ----------------------------------------------------------------------------------------------- filter

hutool-core/src/main/java/cn/hutool/core/text/StrJoiner.java

@@ -9,6 +9,7 @@ import cn.hutool.core.util.ObjUtil;
 import java.io.IOException;
 import java.io.Serializable;
 import java.util.Iterator;
+import java.util.Map;
 import java.util.function.Function;
 
 /**
@@ -196,7 +197,14 @@ public class StrJoiner implements Appendable, Serializable {
 	}
 
 	/**
-	 * 追加对象到拼接器中
+	 * 追加对象到拼接器中，支持：<br>
+	 * <ul>
+	 *     <li>null，按照 {@link #nullMode} 策略追加</li>
+	 *     <li>array，逐个追加</li>
+	 *     <li>{@link Iterator}，逐个追加</li>
+	 *     <li>{@link Iterable}，逐个追加</li>
+	 *     <li>{@link Map.Entry}，追加键，分隔符，再追加值</li>
+	 * </ul>
 	 *
 	 * @param obj 对象，支持数组、集合等
 	 * @return this
@@ -210,6 +218,9 @@ public class StrJoiner implements Appendable, Serializable {
 			append((Iterator<?>) obj);
 		} else if (obj instanceof Iterable) {
 			append(((Iterable<?>) obj).iterator());
+		}else if (obj instanceof Map.Entry) {
+			final Map.Entry<?, ?> entry = (Map.Entry<?, ?>) obj;
+			append(entry.getKey()).append(entry.getValue());
 		} else {
 			append(ObjUtil.toString(obj));
 		}

hutool-core/src/test/java/cn/hutool/core/map/MapJoinerTest.java

@@ -0,0 +1,25 @@
+package cn.hutool.core.map;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class MapJoinerTest {
+
+	@Test
+	public void joinMapTest(){
+		final Dict v1 = Dict.of().set("id", 12).set("name", "张三").set("age", 23);
+		final MapJoiner joiner = MapJoiner.of("+", "-");
+		joiner.append(v1, null);
+
+		Assert.assertEquals("id-12+name-张三+age-23", joiner.toString());
+	}
+
+	@Test
+	public void joinMapWithPredicateTest(){
+		final Dict v1 = Dict.of().set("id", 12).set("name", "张三").set("age", 23);
+		final MapJoiner joiner = MapJoiner.of("+", "-");
+		joiner.append(v1, (entry)->"age".equals(entry.getKey()));
+
+		Assert.assertEquals("age-23", joiner.toString());
+	}
+}

hutool-core/src/test/java/cn/hutool/core/map/MapUtilTest.java

@@ -240,4 +240,11 @@ public class MapUtilTest {
 		Assert.assertTrue(v2s.contains(13));
 		Assert.assertTrue(v2s.contains("李四"));
 	}
+
+	@Test
+	public void joinIgnoreNullTest() {
+		final Dict v1 = Dict.of().set("id", 12).set("name", "张三").set("age", null);
+		final String s = MapUtil.joinIgnoreNull(v1, ",", "=");
+		Assert.assertEquals("id=12,name=张三", s);
+	}
 }