add config

hutool-json/src/main/java/org/dromara/hutool/json/engine/FastJSON2Engine.java

@@ -92,21 +92,26 @@ public class FastJSON2Engine extends AbstractJSONEngine {
 
 	@Override
 	protected void initEngine() {
+		JSONEngineConfig config;
 		if(null == this.readerContext){
 			this.readerContext = JSONFactory.createReadContext();
-			final String dateFormat = ObjUtil.defaultIfNull(this.config, JSONEngineConfig::getDateFormat, "millis");
+
-			this.readerContext.setDateFormat(ObjUtil.defaultIfNull(dateFormat, "millis"));
+			config = ObjUtil.defaultIfNull(this.config, JSONEngineConfig::of);
+			this.readerContext.setDateFormat(ObjUtil.defaultIfNull(config.getDateFormat(), "millis"));
 		}
 		if(null == this.writerContext){
 			final List<JSONWriter.Feature> features = ListUtil.of();
-			if(ObjUtil.defaultIfNull(this.config, JSONEngineConfig::isPrettyPrint, false)){
+			config = ObjUtil.defaultIfNull(this.config, JSONEngineConfig::of);
+			if(config.isPrettyPrint()){
 				features.add(JSONWriter.Feature.PrettyFormat);
 			}
+			if(!config.isIgnoreNullValue()){
+				features.add(JSONWriter.Feature.WriteMapNullValue);
+			}
 			this.writerContext = JSONFactory.createWriteContext(features.toArray(new JSONWriter.Feature[0]));
 
-			// 自定义配置
+			// 自定义其它配置
-			final String dateFormat = ObjUtil.defaultIfNull(this.config, JSONEngineConfig::getDateFormat, "millis");
+			this.writerContext.setDateFormat(ObjUtil.defaultIfNull(config.getDateFormat(), "millis"));
-			this.writerContext.setDateFormat(ObjUtil.defaultIfNull(dateFormat, "millis"));
 		}
 	}
 }

hutool-json/src/main/java/org/dromara/hutool/json/engine/GsonEngine.java

@@ -78,11 +78,13 @@ public class GsonEngine extends AbstractJSONEngine {
 			return;
 		}
 
+		// 自定义配置
+		final JSONEngineConfig config = ObjUtil.defaultIfNull(this.config, JSONEngineConfig::of);
 		final GsonBuilder builder = new GsonBuilder();
-		if (ObjUtil.defaultIfNull(this.config, JSONEngineConfig::isPrettyPrint, false)) {
+		if (config.isPrettyPrint()) {
 			builder.setPrettyPrinting();
 		}
-		final String dateFormat = ObjUtil.apply(this.config, JSONEngineConfig::getDateFormat);
+		final String dateFormat = config.getDateFormat();
 		if (StrUtil.isNotEmpty(dateFormat)) {
 			builder.setDateFormat(dateFormat);
 			builder.registerTypeAdapter(LocalDateTime.class, (JsonDeserializer<LocalDateTime>) (json, typeOfT, context) -> TimeUtil.parse(json.getAsString(), dateFormat));
@@ -95,6 +97,9 @@ public class GsonEngine extends AbstractJSONEngine {
 			builder.registerTypeAdapter(LocalDateTime.class, (JsonDeserializer<LocalDateTime>) (json, typeOfT, context) -> TimeUtil.of(json.getAsJsonPrimitive().getAsLong()));
 			builder.registerTypeAdapter(LocalDateTime.class, (JsonSerializer<LocalDateTime>) (date, type, jsonSerializationContext) -> new JsonPrimitive(TimeUtil.toEpochMilli(date)));
 		}
+		if(!config.isIgnoreNullValue()){
+			builder.serializeNulls();
+		}
 
 		this.gson = builder.create();
 	}

hutool-json/src/main/java/org/dromara/hutool/json/engine/HutoolJSONEngine.java

@@ -64,6 +64,7 @@ public class HutoolJSONEngine extends AbstractJSONEngine {
 		final JSONConfig hutoolSJONConfig = JSONConfig.of();
 		if(null != this.config){
 			hutoolSJONConfig.setDateFormat(this.config.getDateFormat());
+			hutoolSJONConfig.setIgnoreNullValue(this.config.isIgnoreNullValue());
 		}
 
 		this.hutoolSJONConfig = hutoolSJONConfig;

hutool-json/src/main/java/org/dromara/hutool/json/engine/JSONEngineConfig.java

@@ -44,6 +44,10 @@ public class JSONEngineConfig implements Serializable {
 	 * 日期格式，null表示默认的时间戳
 	 */
 	private String dateFormat;
+	/**
+	 * 是否忽略null值
+	 */
+	private boolean ignoreNullValue = true;
 
 	/**
 	 * 获取是否启用格式化输出
@@ -85,4 +89,24 @@ public class JSONEngineConfig implements Serializable {
 		this.dateFormat = dateFormat;
 		return this;
 	}
+
+	/**
+	 * 是否忽略null值
+	 *
+	 * @return 是否忽略null值
+	 */
+	public boolean isIgnoreNullValue() {
+		return this.ignoreNullValue;
+	}
+
+	/**
+	 * 设置是否忽略null值
+	 *
+	 * @param ignoreNullValue 是否忽略null值
+	 * @return this
+	 */
+	public JSONEngineConfig setIgnoreNullValue(final boolean ignoreNullValue) {
+		this.ignoreNullValue = ignoreNullValue;
+		return this;
+	}
 }

hutool-json/src/main/java/org/dromara/hutool/json/engine/JacksonEngine.java

@@ -16,6 +16,7 @@
 
 package org.dromara.hutool.json.engine;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.JavaType;
@@ -112,18 +113,22 @@ public class JacksonEngine extends AbstractJSONEngine {
 			JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES
 		);
 
+		// 支持Java8+日期格式
+		registerModule(mapper, "com.fasterxml.jackson.datatype.jsr310.JavaTimeModule");
+
 		// 自定义配置
-		if (ObjUtil.defaultIfNull(this.config, JSONEngineConfig::isPrettyPrint, false)) {
+		final JSONEngineConfig config = ObjUtil.defaultIfNull(this.config, JSONEngineConfig::of);
+		if(config.isPrettyPrint()){
 			mapper.enable(SerializationFeature.INDENT_OUTPUT);
 		}
-		final String dateFormat = ObjUtil.apply(this.config, JSONEngineConfig::getDateFormat);
+		final String dateFormat = config.getDateFormat();
 		if(StrUtil.isNotEmpty(dateFormat)){
 			mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
 			mapper.setDateFormat(DateUtil.newSimpleFormat(dateFormat));
 		}
-
+		if(config.isIgnoreNullValue()){
-		// 支持Java8+日期格式
+			mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
-		registerModule(mapper, "com.fasterxml.jackson.datatype.jsr310.JavaTimeModule");
+		}
 
 		this.mapper = mapper;
 	}

hutool-json/src/test/java/org/dromara/hutool/json/engine/FastJSONTest.java

@@ -36,4 +36,17 @@ public class FastJSONTest {
 		engine.init(JSONEngineConfig.of().setDateFormat("yyyy-MM-dd HH:mm:ss"));
 		Assertions.assertEquals("{\"date1\":\"2024-01-01 01:12:21\",\"date2\":\"2024-01-01 01:12:21\"}", engine.toJsonString(bean));
 	}
+
+	@Test
+	void writeNullTest() {
+		final BeanWithDate bean = new BeanWithDate(null, null);
+		final JSONEngine engine = JSONEngineFactory.createEngine("fastjson");
+
+		String jsonString = engine.toJsonString(bean);
+		Assertions.assertEquals("{}", jsonString);
+
+		engine.init(JSONEngineConfig.of().setIgnoreNullValue(false));
+		jsonString = engine.toJsonString(bean);
+		Assertions.assertEquals("{\"date1\":null,\"date2\":null}", jsonString);
+	}
 }

hutool-json/src/test/java/org/dromara/hutool/json/engine/GsonTest.java

@@ -37,4 +37,17 @@ public class GsonTest {
 		engine.init(JSONEngineConfig.of().setDateFormat("yyyy-MM-dd HH:mm:ss"));
 		Assertions.assertEquals("{\"date1\":\"2024-01-01 01:12:21\",\"date2\":\"2024-01-01 01:12:21\"}", engine.toJsonString(bean));
 	}
+
+	@Test
+	void writeNullTest() {
+		final BeanWithDate bean = new BeanWithDate(null, null);
+		final JSONEngine engine = JSONEngineFactory.createEngine("gson");
+
+		String jsonString = engine.toJsonString(bean);
+		Assertions.assertEquals("{}", jsonString);
+
+		engine.init(JSONEngineConfig.of().setIgnoreNullValue(false));
+		jsonString = engine.toJsonString(bean);
+		Assertions.assertEquals("{\"date1\":null,\"date2\":null}", jsonString);
+	}
 }

hutool-json/src/test/java/org/dromara/hutool/json/engine/HutoolJSONTest.java

@@ -33,4 +33,17 @@ public class HutoolJSONTest {
 		engine.init(JSONEngineConfig.of().setDateFormat("yyyy-MM-dd HH:mm:ss"));
 		Assertions.assertEquals("{\"date1\":\"2024-01-01 01:12:21\",\"date2\":\"2024-01-01 01:12:21\"}", engine.toJsonString(bean));
 	}
+
+	@Test
+	void writeNullTest() {
+		final BeanWithDate bean = new BeanWithDate(null, null);
+		final JSONEngine engine = JSONEngineFactory.createEngine("hutool");
+
+		String jsonString = engine.toJsonString(bean);
+		Assertions.assertEquals("{}", jsonString);
+
+		engine.init(JSONEngineConfig.of().setIgnoreNullValue(false));
+		jsonString = engine.toJsonString(bean);
+		Assertions.assertEquals("{\"date1\":null,\"date2\":null}", jsonString);
+	}
 }

hutool-json/src/test/java/org/dromara/hutool/json/engine/JacksonTest.java

@@ -40,4 +40,17 @@ public class JacksonTest {
 		engine.init(JSONEngineConfig.of().setDateFormat("yyyy-MM-dd HH:mm:ss"));
 		Assertions.assertEquals("{\"date1\":\"2024-01-01 01:12:21\",\"date2\":\"2024-01-01T01:12:21\"}", engine.toJsonString(bean));
 	}
+
+	@Test
+	void writeNullTest() {
+		final BeanWithDate bean = new BeanWithDate(null, null);
+		final JSONEngine engine = JSONEngineFactory.createEngine("jackson");
+
+		String jsonString = engine.toJsonString(bean);
+		Assertions.assertEquals("{}", jsonString);
+
+		engine.init(JSONEngineConfig.of().setIgnoreNullValue(false));
+		jsonString = engine.toJsonString(bean);
+		Assertions.assertEquals("{\"date1\":null,\"date2\":null}", jsonString);
+	}
 }