完美解决json循环问题（使用javassist增强）：Spring MVC中使用jackson的MixInAnnotations方法动态过滤JSON字段
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问题描述
项目使用SpringMVC框架，并用jackson库处理JSON和POJO的转换。在POJO转化成JSON时，有些属性我们不需要输出或者有些属性循环引用会造成无法输出。
例如：实体User其中包括用户名、密码、邮箱等，但是我们在输出用户信息不希望输出密码、邮箱信息;
例如：实体user和department是多对一的关系，user内保存着department的信息，那么json输出时会导致这两个实体数据的循环输出;
jackson默认可以使用JsonIgnoreProperties接口来定义要过滤的属性,然后使用ObjectMapper#addMixInAnnotations来设置对应实体对应的JsonIgnoreProperties接口,这样就能达到过滤的目的。可是这样很不爽,因为如果你对n个实体对应有m种过滤需求就至少要建n*m个JsonIgnoreProperties接口。
解决方案
主要逻辑如下图
大致处理流程:
1、使用自定义注解controller方法
2、然后定义aop捕获所有controller方法
3、当aop捕获到controller方法时调用JavassistFilterPropertyHandler#filterProperties方法;
4、filterProperties读取注解并根据自定义注解使用javassist创建JsonIgnoreProperties临时实现类(同时缓存到map内,下次可直接取出)并存入当前线程内(ThreadJacksonMixInHolder, 使用threadlocal实现),
5、在springmvc输出json的类内自定义ObjectMapper, 从当前线程内取出JsonIgnoreProperties临时类, 调用ObjectMapper# addMixInAnnotations使之起效
6、最后使用ObjectMapper输出
用法:
1、定义aop, 用来捕获springmvc的controller方法,
package com.xiongyingqi.json.filter.aop;import com.xiongyingqi.jackson.FilterPropertyHandler;import com.xiongyingqi.jackson.impl.JavassistFilterPropertyHandler;import org.apache.log4j.Logger;import org.aspectj.lang.ProceedingJoinPoint;import org.aspectj.lang.annotation.AfterThrowing;import org.aspectj.lang.annotation.Around;import org.aspectj.lang.annotation.Aspect;import org.aspectj.lang.annotation.Pointcut;import org.aspectj.lang.reflect.MethodSignature;import java.lang.reflect.Method;/** * @author 瑛琪 <a href="http://xiongyingqi.com">xiongyingqi.com</a> * @version 2013-9-27 下午5:41:12 */@Aspectpublic class IgnorePropertyAspect { public static final Logger LOGGER = Logger.getLogger(IgnorePropertyAspect.class); @Pointcut("execution(* com.kingray.web.*.*(..))") private void anyMethod() { } @Around("anyMethod()") public Object around(ProceedingJoinPoint pjp) throws Throwable { Object returnVal = pjp.proceed(); // 返回源结果 try { FilterPropertyHandler filterPropertyHandler = new JavassistFilterPropertyHandler(true); Method method = ((MethodSignature) pjp.getSignature()).getMethod(); returnVal = filterPropertyHandler.filterProperties(method, returnVal); } catch (Exception e) { LOGGER.error(e); e.printStackTrace(); } return returnVal; } @AfterThrowing(pointcut = "anyMethod()", throwing = "e") public void doAfterThrowing(Exception e) { System.out.println(" -------- AfterThrowing -------- "); }}spring配置:
<!-- 启动mvc对aop的支持,使用aspectj代理 --><aop:aspectj-autoproxyproxy-target-class="true" /><beanid="ignorePropertyAspect" class="com.xiongyingqi.json.filter.aop.IgnorePropertyAspect"></bean>
2、配置spring-mvc的messageconverter
<pre name="code" class="java"><beanclass="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"><property name="cacheSeconds" value="0" /><!--日期格式转换 --><property name="webBindingInitializer"><bean class="com.kingray.spring.http.convert.DateConverter" /></property><property name="messageConverters"><list><beanclass="com.xiongyingqi.spring.http.convert.json.Jackson2HttpMessageConverter"></bean><beanclass="com.xiongyingqi.spring.http.convert.json.JacksonHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.BufferedImageHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.ResourceHttpMessageConverter"></bean><bean class="org.springframework.http.converter.FormHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.feed.AtomFeedHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.feed.RssChannelHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.xml.Jaxb2CollectionHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.xml.SourceHttpMessageConverter"></bean><beanclass="org.springframework.http.converter.ByteArrayHttpMessageConverter"></bean></list></property></bean>
3、重写spring的MappingJackson2HttpMessageConverter类,这样输出的json内容就能自定义
package com.xiongyingqi.spring.http.convert.json;import java.io.IOException;import com.xiongyingqi.jackson.helper.ThreadJacksonMixInHolder;import org.springframework.http.HttpOutputMessage;import org.springframework.http.converter.HttpMessageNotWritableException;import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;import com.fasterxml.jackson.core.JsonEncoding;import com.fasterxml.jackson.core.JsonGenerator;import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.ObjectMapper;import com.fasterxml.jackson.databind.SerializationFeature;/** * @author 瑛琪 <a href="http://xiongyingqi.com">xiongyingqi.com</a> * @version 2013-9-27 下午4:05:46 */public class Jackson2HttpMessageConverter extends MappingJackson2HttpMessageConverter { private ObjectMapper objectMapper = new ObjectMapper(); private boolean prefixJson = false; /** * <br> * 2013-9-27 下午4:10:28 * * @see org.springframework.http.converter.json.MappingJacksonHttpMessageConverter#writeInternal(Object, * org.springframework.http.HttpOutputMessage) */ @Override protected void writeInternal(Object object, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException { // super.writeInternal(object, outputMessage); // 判断是否需要重写objectMapper ObjectMapper objectMapper = this.objectMapper;// 本地化ObjectMapper，防止方法级别的ObjectMapper改变全局ObjectMapper if (ThreadJacksonMixInHolder.isContainsMixIn()) { objectMapper = ThreadJacksonMixInHolder.builderMapper(); } JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType()); JsonGenerator jsonGenerator = objectMapper.getFactory().createGenerator( outputMessage.getBody(), encoding); // A workaround for JsonGenerators not applying serialization features // https://github.com/FasterXML/jackson-databind/issues/12 if (objectMapper.isEnabled(SerializationFeature.INDENT_OUTPUT)) { jsonGenerator.useDefaultPrettyPrinter(); } try { if (this.prefixJson) { jsonGenerator.writeRaw("{} && "); } objectMapper.writeValue(jsonGenerator, object); } catch (JsonProcessingException ex) { throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex); } // JsonEncoding encoding = // getJsonEncoding(outputMessage.getHeaders().getContentType()); // JsonGenerator jsonGenerator = // this.objectMapper.getJsonFactory().createJsonGenerator(outputMessage.getBody(), // encoding); // // // A workaround for JsonGenerators not applying serialization // features // // https://github.com/FasterXML/jackson-databind/issues/12 // if (this.objectMapper.isEnabled(SerializationFeature.INDENT_OUTPUT)) // { // jsonGenerator.useDefaultPrettyPrinter(); // } // // try { // if (this.prefixJson) { // jsonGenerator.writeRaw("{} && "); // } // this.objectMapper.writeValue(jsonGenerator, object); // } // catch (JsonProcessingException ex) { // throw new HttpMessageNotWritableException("Could not write JSON: " + // ex.getMessage(), ex); // } } public boolean isPrefixJson() { return prefixJson; } public void setPrefixJson(boolean prefixJson) { this.prefixJson = prefixJson; }}4、在方法上注解
以下是Controller方法的示例，yxResourceSelfRelationsForSuperiorResourceId是YxResource内要过滤的属性:
@IgnoreProperties(value= { @IgnoreProperty(pojo = YxResource.class, name = { "yxResourceSelfRelationsForSuperiorResourceId"})}) @RequestMapping(value = "/{resourceId}", method = RequestMethod.GET) @ResponseBody public Object getResourceByResourceId(@PathVariable Integer resourceId) { YxResource resource = resourceService.getResource(resourceId); return resource; }主要类说明
1、自定义注解类：这些类是用于注解实体类输出json时要注解过滤的属性
IgnoreProperties.java 用于同时注解IgnoreProperty和AllowProperty
package com.xiongyingqi.jackson.annotation;import java.lang.annotation.*;/** * json属性过滤注解，对于同一个pojo来说 @AllowProperty 是与 @IgnoreProperty 是冲突的，如果这两个注解注解了<br> * 例如以下代码YxResource实体只会显示resourceName和resourceDescribe属性 * <p/> * <pre> * @IgnoreProperties( * value = { * @IgnoreProperty( * pojo = YxResource.class, * name = { * "yxResourceDataRelations", * "yxResourceSelfRelationsForSublevelResourceId", * "yxPermisionResourceRelations" }), * @IgnoreProperty( * pojo = YxResourceSelfRelation.class, * name = { * "yxResourceBySuperiorResourceId", * "id" }) * }, * allow = { * @AllowProperty( * pojo = YxResource.class, * name = { "<b><i>resourceName</i></b>" }) }) * @AllowProperty( * pojo = YxResource.class, * name = { "<b><i>resourceDescribe</i></b>" }) * </pre> * <p/> * <p/> * 但是，对于同一个pojo的同一属性来说@AllowProperty是与@IgnoreProperty则会按照@IgnoreProperty过滤的属性名过滤 * 例如以下代码YxResource实体不会显示resourceName属性的值 * <p/> * <pre> * @IgnoreProperties( * value = { * @IgnoreProperty( * pojo = YxResource.class, * name = { "<b><i>resourceName</i></b>", * "yxResourceDataRelations", * "yxResourceSelfRelationsForSublevelResourceId", * "yxPermisionResourceRelations" }), * @IgnoreProperty( * pojo = YxResourceSelfRelation.class, * name = { * "yxResourceBySuperiorResourceId", * "id" }) * }, * allow = { * @AllowProperty( * pojo = YxResource.class, * name = { "<b><i>resourceName</i></b>" }) }) * </pre> * * @author 瑛琪 <a href="http://xiongyingqi.com">xiongyingqi.com</a> * @version 2013-9-27 下午4:18:39 */@Documented@Target({ElementType.TYPE, ElementType.METHOD})@Retention(RetentionPolicy.RUNTIME)public @interface IgnoreProperties { /** * 要过滤的属性 * * @return */ IgnoreProperty[] value() default @IgnoreProperty(pojo = Object.class, name = ""); /** * 允许的属性 * * @return */ AllowProperty[] allow() default @AllowProperty(pojo = Object.class, name = "");}IgnoreProperty.java ：过滤指定对象内的指定字段名
package com.xiongyingqi.jackson.annotation;import java.lang.annotation.*;/** * 用于注解json过滤pojo内的属性，其他的属性都会被序列化成字符串 * * @author 瑛琪 <a href="http://xiongyingqi.com">xiongyingqi.com</a> * @version 2013-9-27 下午4:24:33 */@Documented@Target({ElementType.TYPE, ElementType.METHOD, ElementType.ANNOTATION_TYPE})@Retention(RetentionPolicy.RUNTIME)public @interface IgnoreProperty { /** * 要忽略字段的POJO <br> * 2013-9-27 下午4:27:08 * * @return */ Class<?> pojo(); /** * 要忽略的字段名 <br> * 2013-9-27 下午4:27:12 * * @return */ String[] name(); /** * 字段名，无论是哪种 <br> * 2013-9-27 下午4:27:15 * * @return */ //String value() default ""; /** * 最大迭代层次<br> * 当注解了pojo和name值时，该值表示遍历bean属性的最大曾次数，此注解一般用于自关联的bean类， * 如果循环层次大于等于maxLevel时则不再读取属性<br> * 如果maxIterationLevel为0，则不限制迭代层次<br> * 如果maxIterationLevel为1，则迭代读取属性一次<br> * 2013-10-21 下午2:16:26 * * @return */ //int maxIterationLevel() default 0;}AllowProperty.java：注解实体类允许的字段
package com.xiongyingqi.jackson.annotation;import java.lang.annotation.*;/** * 只允许pojo内的属性序列化成json，对于同一个pojo该注解是与IgnoreProperty是冲突的<br> * * @author 瑛琪 <a href="http://xiongyingqi.com">xiongyingqi.com</a> * @version 2013-10-30 下午3:57:35 */@Documented@Target({ElementType.TYPE, ElementType.METHOD, ElementType.ANNOTATION_TYPE})@Retention(RetentionPolicy.RUNTIME)public @interface AllowProperty { /** * 目标POJO <br> * 2013-9-27 下午4:27:08 * * @return */ Class<?> pojo(); /** * 允许序列化的属性名 <br> * 2013-9-27 下午4:27:12 * * @return */ String[] name();}2、核心处理类，用于处理自定义注解并将生成的类存入当前线程
package com.xiongyingqi.jackson.impl;import com.fasterxml.jackson.annotation.JsonIgnoreProperties;import com.fasterxml.jackson.core.JsonEncoding;import com.fasterxml.jackson.databind.ObjectMapper;import com.xiongyingqi.jackson.FilterPropertyHandler;import com.xiongyingqi.jackson.annotation.AllowProperty;import com.xiongyingqi.jackson.annotation.IgnoreProperties;import com.xiongyingqi.jackson.annotation.IgnoreProperty;import com.xiongyingqi.jackson.helper.ThreadJacksonMixInHolder;import com.xiongyingqi.util.EntityHelper;import com.xiongyingqi.util.StringHelper;import javassist.CannotCompileException;import javassist.ClassPool;import javassist.CtClass;import javassist.bytecode.AnnotationsAttribute;import javassist.bytecode.ClassFile;import javassist.bytecode.ConstPool;import javassist.bytecode.annotation.*;import org.apache.log4j.Logger;import org.springframework.http.MediaType;import org.springframework.web.bind.annotation.ResponseBody;import java.lang.reflect.Method;import java.nio.charset.Charset;import java.util.*;import java.util.Map.Entry;//@IgnoreProperty(pojo = YxUserRoleRelation.class, name = { "id", "yxUser" })/** * 使用代理来创建jackson的MixInAnnotation注解接口<br> * 如果使用本实现方法，一定要配置在web.xml中配置过滤器WebContextFilter，否则无法输出json到客户端 * * @author 瑛琪 <a href="http://xiongyingqi.com">xiongyingqi.com</a> * @version 2013-10-25 下午2:31:21 */public class JavassistFilterPropertyHandler implements FilterPropertyHandler { public static final Logger LOGGER = Logger.getLogger(JavassistFilterPropertyHandler.class); /** * 注解的方法对应生成的代理类映射表 */ private static Map<Method, Map<Class<?>, Class<?>>> proxyMethodMap = new HashMap<Method, Map<Class<?>, Class<?>>>(); /** * String数组的hashCode与生成的对应的代理类的映射表 */ private static Map<Integer, Class<?>> proxyMixInAnnotationMap = new HashMap<Integer, Class<?>>(); private static String[] globalIgnoreProperties = new String[]{"hibernateLazyInitializer", "handler" }; /** * 如果是标注的SpringMVC中的Controller方法，则应判断是否注解了@ResponseBody */ private boolean isResponseBodyAnnotation; /** * 创建代理接口的唯一值索引 */ private static int proxyIndex; public JavassistFilterPropertyHandler() { } public JavassistFilterPropertyHandler(String[] globalIgnoreProperties) { JavassistFilterPropertyHandler.globalIgnoreProperties = globalIgnoreProperties; } /** * @param isResponseBodyAnnotation 如果是标注的SpringMVC中的Controller方法，则应判断是否注解了@ResponseBody */ public JavassistFilterPropertyHandler(boolean isResponseBodyAnnotation) { this.isResponseBodyAnnotation = isResponseBodyAnnotation; } /** * <br> * 2013-10-28 上午11:11:24 * * @param collection * @param names * @return */ private Collection<String> checkAndPutToCollection(Collection<String> collection, String[] names) { if (collection == null) { collection = new HashSet<String>(); } Collections.addAll(collection, names); return collection; } private Collection<String> putGlobalIgnoreProperties(Collection<String> collection) { if (globalIgnoreProperties != null) { if (collection == null) { collection = new HashSet<String>(); } for (int i = 0; i < globalIgnoreProperties.length; i++) { String name = globalIgnoreProperties[i]; collection.add(name); } } return collection; } /** * 处理IgnoreProperties注解 <br> * 2013-10-30 下午6:15:41 * * @param properties * @param pojoAndNamesMap */ private void processIgnorePropertiesAnnotation(IgnoreProperties properties, Map<Class<?>, Collection<String>> pojoAndNamesMap) { IgnoreProperty[] values = properties.value(); AllowProperty[] allowProperties = properties.allow(); if (allowProperties != null) { for (AllowProperty allowProperty : allowProperties) { processAllowPropertyAnnotation(allowProperty, pojoAndNamesMap); } } if (values != null) { for (IgnoreProperty property : values) { processIgnorePropertyAnnotation(property, pojoAndNamesMap); } } } /** * 处理IgnoreProperty注解 <br> * 2013-10-30 下午6:16:08 * * @param property * @param pojoAndNamesMap */ private void processIgnorePropertyAnnotation(IgnoreProperty property, Map<Class<?>, Collection<String>> pojoAndNamesMap) { String[] names = property.name(); Class<?> pojoClass = property.pojo(); // Class<?> proxyAnnotationInterface = createMixInAnnotation(names);// // 根据注解创建代理接口 Collection<String> nameCollection = pojoAndNamesMap.get(pojoClass); nameCollection = checkAndPutToCollection(nameCollection, names); pojoAndNamesMap.put(pojoClass, nameCollection); } /** * 处理AllowProperty注解 <br> * 2013-10-30 下午6:16:08 * * @param property * @param pojoAndNamesMap */ private void processAllowPropertyAnnotation(AllowProperty property, Map<Class<?>, Collection<String>> pojoAndNamesMap) { String[] allowNames = property.name(); Class<?> pojoClass = property.pojo(); Collection<String> ignoreProperties = EntityHelper .getUnstaticClassFieldNameCollection(pojoClass); Collection<String> allowNameCollection = new ArrayList<String>(); Collections.addAll(allowNameCollection, allowNames); Collection<String> nameCollection = pojoAndNamesMap.get(pojoClass); if (nameCollection != null) { nameCollection.removeAll(allowNameCollection); } else { ignoreProperties.removeAll(allowNameCollection); nameCollection = ignoreProperties; } pojoAndNamesMap.put(pojoClass, nameCollection); } /** * 根据方法获取过滤映射表 <br> * 2013-10-25 下午2:47:34 * * @param method 注解了 @IgnoreProperties 或 @IgnoreProperty 的方法（所在的类） * @return Map<Class<?>, Collection<Class<?>>> pojo与其属性的映射表 */ public Map<Class<?>, Class<?>> getProxyMixInAnnotation(Method method) { if (isResponseBodyAnnotation && !method.isAnnotationPresent(ResponseBody.class)) { return null; } Map<Class<?>, Class<?>> map = proxyMethodMap.get(method);// 从缓存中查找是否存在 if (map != null && map.entrySet().size() > 0) {// 如果已经读取该方法的注解信息，则从缓存中读取 return map; } else { map = new HashMap<Class<?>, Class<?>>(); } Class<?> clazzOfMethodIn = method.getDeclaringClass();// 方法所在的class Map<Class<?>, Collection<String>> pojoAndNamesMap = new HashMap<Class<?>, Collection<String>>(); IgnoreProperties classIgnoreProperties = clazzOfMethodIn .getAnnotation(IgnoreProperties.class); IgnoreProperty classIgnoreProperty = clazzOfMethodIn.getAnnotation(IgnoreProperty.class); AllowProperty classAllowProperty = clazzOfMethodIn.getAnnotation(AllowProperty.class); IgnoreProperties ignoreProperties = method.getAnnotation(IgnoreProperties.class); IgnoreProperty ignoreProperty = method.getAnnotation(IgnoreProperty.class); AllowProperty allowProperty = method.getAnnotation(AllowProperty.class); if (allowProperty != null) {// 方法上的AllowProperty注解 processAllowPropertyAnnotation(allowProperty, pojoAndNamesMap); } if (classAllowProperty != null) { processAllowPropertyAnnotation(classAllowProperty, pojoAndNamesMap); } if (classIgnoreProperties != null) {// 类上的IgnoreProperties注解 processIgnorePropertiesAnnotation(classIgnoreProperties, pojoAndNamesMap); } if (classIgnoreProperty != null) {// 类上的IgnoreProperty注解 processIgnorePropertyAnnotation(classIgnoreProperty, pojoAndNamesMap); } if (ignoreProperties != null) {// 方法上的IgnoreProperties注解 processIgnorePropertiesAnnotation(ignoreProperties, pojoAndNamesMap); } if (ignoreProperty != null) {// 方法上的IgnoreProperties注解 processIgnorePropertyAnnotation(ignoreProperty, pojoAndNamesMap); } Set<Entry<Class<?>, Collection<String>>> entries = pojoAndNamesMap.entrySet(); for (Iterator<Entry<Class<?>, Collection<String>>> iterator = entries.iterator(); iterator .hasNext(); ) { Entry<Class<?>, Collection<String>> entry = (Entry<Class<?>, Collection<String>>) iterator .next(); Collection<String> nameCollection = entry.getValue(); nameCollection = putGlobalIgnoreProperties(nameCollection);// 将全局过滤字段放入集合内 String[] names = nameCollection.toArray(new String[]{}); // EntityHelper.print(entry.getKey()); // for (int i = 0; i < names.length; i++) { // String name = names[i]; // EntityHelper.print(name); // } Class<?> clazz = createMixInAnnotation(names); map.put(entry.getKey(), clazz); } proxyMethodMap.put(method, map); return map; } /** * 创建jackson的代理注解接口类 <br> * 2013-10-25 上午11:59:50 * * @param names 要生成的字段 * @return 代理接口类 */ private Class<?> createMixInAnnotation(String[] names) { Class<?> clazz = null; clazz = proxyMixInAnnotationMap.get(StringHelper.hashCodeOfStringArray(names)); if (clazz != null) { return clazz; } ClassPool pool = ClassPool.getDefault(); // 创建代理接口 CtClass cc = pool.makeInterface("ProxyMixInAnnotation" + System.currentTimeMillis() + proxyIndex++); ClassFile ccFile = cc.getClassFile(); ConstPool constpool = ccFile.getConstPool(); // create the annotation AnnotationsAttribute attr = new AnnotationsAttribute(constpool, AnnotationsAttribute.visibleTag); // 创建JsonIgnoreProperties注解 Annotation jsonIgnorePropertiesAnnotation = new Annotation( JsonIgnoreProperties.class.getName(), constpool); BooleanMemberValue ignoreUnknownMemberValue = new BooleanMemberValue(false, constpool); ArrayMemberValue arrayMemberValue = new ArrayMemberValue(constpool);// value的数组成员 Collection<MemberValue> memberValues = new HashSet<MemberValue>(); for (int i = 0; i < names.length; i++) { String name = names[i]; StringMemberValue memberValue = new StringMemberValue(constpool);// 将name值设入注解内 memberValue.setValue(name); memberValues.add(memberValue); } arrayMemberValue.setValue(memberValues.toArray(new MemberValue[]{})); jsonIgnorePropertiesAnnotation.addMemberValue("value", arrayMemberValue); jsonIgnorePropertiesAnnotation.addMemberValue("ignoreUnknown", ignoreUnknownMemberValue); attr.addAnnotation(jsonIgnorePropertiesAnnotation); ccFile.addAttribute(attr); // generate the class try { clazz = cc.toClass(); proxyMixInAnnotationMap.put(StringHelper.hashCodeOfStringArray(names), clazz); // JsonIgnoreProperties ignoreProperties = (JsonIgnoreProperties) // clazz // .getAnnotation(JsonIgnoreProperties.class); // EntityHelper.print(ignoreProperties); // // EntityHelper.print(clazz); // try { // Object instance = clazz.newInstance(); // EntityHelper.print(instance); // // } catch (InstantiationException e) { // e.printStackTrace(); // } catch (IllegalAccessException e) { // e.printStackTrace(); // } } catch (CannotCompileException e) { e.printStackTrace(); } // right // mthd.getMethodInfo().addAttribute(attr); return clazz; } @Override public Object filterProperties(Method method, Object object) { Map<Class<?>, Class<?>> map = getProxyMixInAnnotation(method); if (map == null || map.entrySet().size() == 0) {// 如果该方法上没有注解，则返回原始对象 return object; }//Set<Entry<Class<?>, Class<?>>> entries = map.entrySet();//for (Iterator<Entry<Class<?>, Class<?>>> iterator = entries.iterator(); iterator.hasNext();) {//Entry<Class<?>, Class<?>> entry = (Entry<Class<?>, Class<?>>) iterator.next();////EntityHelper.print(entry.getKey());//Class<?> clazz = entry.getValue();////EntityHelper.print(clazz.getAnnotation(JsonIgnoreProperties.class));//}//ObjectMapper mapper = createObjectMapper(map); ThreadJacksonMixInHolder.addMixIns(getEntries(map));//try {//HttpServletResponse response = WebContext.getInstance().getResponse();//writeJson(mapper, response, object);//} catch (WebContextAlreadyClearedException e) {//e.printStackTrace();//} return object; } public Set<Entry<Class<?>, Class<?>>> getEntries(Map<Class<?>, Class<?>> map) { Set<Entry<Class<?>, Class<?>>> entries = map.entrySet(); return entries; } /** * 根据指定的过滤表创建jackson对象 <br> * 2013-10-25 下午2:46:43 * * @param map 过滤表 * @return ObjectMapper */ private ObjectMapper createObjectMapper(Map<Class<?>, Class<?>> map) { ObjectMapper mapper = new ObjectMapper(); Set<Entry<Class<?>, Class<?>>> entries = map.entrySet(); for (Iterator<Entry<Class<?>, Class<?>>> iterator = entries.iterator(); iterator.hasNext(); ) { Entry<Class<?>, Class<?>> entry = iterator.next(); mapper.addMixInAnnotations(entry.getKey(), entry.getValue()); } return mapper; } /** * 根据方法上的注解生成objectMapper * * @param method * @return */ public ObjectMapper createObjectMapper(Method method) { return createObjectMapper(getProxyMixInAnnotation(method)); }// /**// * 将结果输出到response <br>// * 2013-10-25 下午2:28:40// *// * @param objectMapper// * @param response// * @param object// */// private void writeJson(ObjectMapper objectMapper, HttpServletResponse response, Object object) {// response.setContentType("application/json");//// JsonEncoding encoding = getJsonEncoding(response.getCharacterEncoding());// JsonGenerator jsonGenerator = null;// try {// jsonGenerator = objectMapper.getJsonFactory().createJsonGenerator(// response.getOutputStream(), encoding);// } catch (IOException e1) {// e1.printStackTrace();// }//// // A workaround for JsonGenerators not applying serialization features// // https://github.com/FasterXML/jackson-databind/issues/12// if (objectMapper.isEnabled(SerializationFeature.INDENT_OUTPUT)) {// jsonGenerator.useDefaultPrettyPrinter();// }//// try {// objectMapper.writeValue(jsonGenerator, object);// } catch (JsonProcessingException ex) {// LOGGER.error(ex);//// throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(),// ex);// } catch (IOException e) {// LOGGER.error(e);// // e.printStackTrace();// }//// } /** * <br> * 2013-10-25 下午12:29:58 * * @param characterEncoding * @return */ private JsonEncoding getJsonEncoding(String characterEncoding) { for (JsonEncoding encoding : JsonEncoding.values()) { if (characterEncoding.equals(encoding.getJavaName())) { return encoding; } } return JsonEncoding.UTF8; } /** * Determine the JSON encoding to use for the given content type. * * @param contentType the media type as requested by the caller * @return the JSON encoding to use (never {@code null}) */ protected JsonEncoding getJsonEncoding(MediaType contentType) { if (contentType != null && contentType.getCharSet() != null) { Charset charset = contentType.getCharSet(); for (JsonEncoding encoding : JsonEncoding.values()) { if (charset.name().equals(encoding.getJavaName())) { return encoding; } } } return JsonEncoding.UTF8; }}package com.xiongyingqi.jackson.helper;import com.fasterxml.jackson.databind.ObjectMapper;import java.util.HashSet;import java.util.Map;import java.util.Set;/** * 在当前线程内保存ObjectMapper供Jackson2HttpMessageConverter使用 * Created by 瑛琪<a href="http://xiongyingqi.com">xiongyingqi.com</a> on 2014/4/1 0001. */public class ThreadJacksonMixInHolder { private static ThreadLocal<ThreadJacksonMixInHolder> holderThreadLocal = new ThreadLocal<ThreadJacksonMixInHolder>(); private Set<Map.Entry<Class<?>, Class<?>>> mixIns; private ObjectMapper mapper; private org.codehaus.jackson.map.ObjectMapper codehausMapper; /** * 根据当前MixIn集合生成objectMapper<p> * <p/> * <b>注意：该方法在返回mapper对象之后调用clear方法，如果再次调用builderMapper()肯定会保存</b> * * @return */ public static ObjectMapper builderMapper() { ThreadJacksonMixInHolder holder = holderThreadLocal.get(); if (holder.mapper == null && isContainsMixIn()) { holder.mapper = new ObjectMapper(); for (Map.Entry<Class<?>, Class<?>> mixIn : holder.mixIns) { holder.mapper.addMixInAnnotations(mixIn.getKey(), mixIn.getValue()); } } clear();// 如果不调用clear可能导致线程内的数据是脏的！ return holder.mapper; } /** * 根据当前MixIn集合生成objectMapper * * @return */ public static org.codehaus.jackson.map.ObjectMapper builderCodehausMapper() { ThreadJacksonMixInHolder holder = holderThreadLocal.get(); if (holder.codehausMapper == null && isContainsMixIn()) { holder.codehausMapper = new org.codehaus.jackson.map.ObjectMapper(); for (Map.Entry<Class<?>, Class<?>> mixIn : holder.mixIns) { holder.codehausMapper.getDeserializationConfig().addMixInAnnotations(mixIn.getKey(), mixIn.getValue()); holder.codehausMapper.getSerializationConfig().addMixInAnnotations(mixIn.getKey(), mixIn.getValue()); } } clear();// 如果不调用clear可能导致线程内的数据是脏的！ return holder.codehausMapper; } /** * 清除当前线程内的数据 */ public static void clear() { holderThreadLocal.set(null);// holderThreadLocal.remove(); } /** * 设置MixIn集合到线程内，如果线程内已经存在数据，则会先清除 * * @param resetMixIns */ public static void setMixIns(Set<Map.Entry<Class<?>, Class<?>>> resetMixIns) { ThreadJacksonMixInHolder holder = holderThreadLocal.get(); if (holder == null) { holder = new ThreadJacksonMixInHolder(); holderThreadLocal.set(holder); } holder.mixIns = resetMixIns; } /** * 不同于setMixIns，addMixIns为增加MixIn集合到线程内，即不会清除已经保存的数据 * <br>2014年4月4日 下午12:08:15 * * @param toAddMixIns */ public static void addMixIns(Set<Map.Entry<Class<?>, Class<?>>> toAddMixIns) { ThreadJacksonMixInHolder holder = holderThreadLocal.get(); if (holder == null) { holder = new ThreadJacksonMixInHolder(); holderThreadLocal.set(holder); } if (holder.mixIns == null) { holder.mixIns = new HashSet<Map.Entry<Class<?>, Class<?>>>(); } holder.mixIns.addAll(toAddMixIns); } /** * 获取线程内的MixIn集合<p></p> * <b>注意：为了防止线程执行完毕之后仍然存在有数据，请务必适时调用clear()方法</b> * * @return * @see com.xiongyingqi.jackson.helper.ThreadJacksonMixInHolder#builderMapper() * @see com.xiongyingqi.jackson.helper.ThreadJacksonMixInHolder#builderCodehausMapper() * @see com.xiongyingqi.jackson.helper.ThreadJacksonMixInHolder#clear() */ public static Set<Map.Entry<Class<?>, Class<?>>> getMixIns() { ThreadJacksonMixInHolder holder = holderThreadLocal.get(); return holder.mixIns; } /** * 判断当前线程是否存在MixIn集合 * * @return */ public static boolean isContainsMixIn() { if (holderThreadLocal.get() == null) { return false; } if (holderThreadLocal.get().mixIns != null && holderThreadLocal.get().mixIns.size() > 0) { return true; } return false; }}性能
1、主要是在map内存储了Javassist的临时类，每个注解(IgnoreProperties等)的方法的调用，对应在FilterPropertyHandler会处理一次注解并在内存内产生一个Javassist临时类，但是访问过一次之后该类就会读取map缓存
2、ThreadJacksonMixInHolder：这个类的原理就是使用ThreadLocal在当前线程内存储处理过的annotation注解，java的容器或框架都是使用了该类，导致的效率问题应该不大
3、未知的bug
其他说明
其他框架内使用
如果不是spring-mvc框架也能使用这些代码来解决，只是必须要修改aop的捕获方法、使用new JavassistFilterPropertyHandler(false)禁用ResponseBody，以及在ObjectMapper输出使用自己定义的输出
源代码地址
github
建议签出github上的代码作为maven依赖，否则请copy需要的代码~
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