我遇到了我的User对象的Jackson序列化问题.
有一些私人领域有getter和setter.当我做这样的事情时,一切正常：
public String json() {
MyUser user = new MyUser();
user.setUsername("myName");
return mapper.writeValueAsString(user); // Valid JSON
}
但是我想用Spring Framework自动装配User对象：
@Autowired
private MyUser user;
public String json() {
System.out.println(user.getUsername()); // Property set before and it works
return mapper.writeValueAsString(user); // Error
}
这不起作用.我有一个错误：
com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.apache.juli.OneLineFormatter and no properties discovered to create BeanSerializer (to avoid exception,disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: com.piggymetrics.classes.PiggyUser$$EnhancerBySpringCGLIB$$5f23855e["targetSource"]->org.springframework.aop.target.SimpleBeanTargetSource["beanFactory"]->org.springframework.beans.factory.support.DefaultListableBeanFactory["parentBeanFactory"]->org.springframework.beans.factory.support.DefaultListableBeanFactory["beanClassLoader"]->org.apache.catalina.loader.WebappClassLoader["resources"]->org.apache.catalina.webresources.StandardRoot["context"]->org.apache.catalina.core.StandardContext["logger"]->org.apache.juli.logging.DirectJDKLog["logger"]->java.util.logging.Logger["parent"]->java.util.logging.Logger["handlers"]->org.apache.juli.AsyncFileHandler["formatter"])
at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:59)
at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:26)
当我试图忽略这些未知错误时
mapper.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);
我得到了无限递归：
com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: org.apache.catalina.core.StandardEngineValve["container"]->org.apache.catalina.core.StandardEngine["pipeline"]->org.apache.catalina.core.StandardPipeline["basic"]->org.apache.catalina.core.StandardEngineValve["container"]
...
看起来Spring在自动装配的MyUser实例上做错了,所以杰克逊无法将其序列化.
有办法解决吗？
UPDATE
MyUser类非常简单：
package com.metrics.classes;
import com.metrics.classes.interfaces.User;
import org.springframework.context.annotation.Scope;
import org.springframework.context.annotation.ScopedProxyMode;
import org.springframework.stereotype.Component;
@Component
@Scope(value = "session",proxyMode = ScopedProxyMode.TARGET_CLASS)
public class MyUser implements User {
private String username;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
}
由于您使用MyUser作为Spring托管bean,因此Spring将您的对象包装到代理中 – 因此当您调用mapper.writeValueAsString(user)时;你实际上是通过代理作为参数.所述代理包含一些属性,即映射器无法序列化.
您可以尝试在序列化之前应用过滤器以仅包含所需的属性：
ObjectMapper mapper = new ObjectMapper();
SimpleFilterProvider simpleFilterProvider = new SimpleFilterProvider()
.addFilter("myUser",simpleBeanPropertyFilter.filterOutAllExcept("username"));
mapper.setFilters(filterProvider);
return mapper.writeValueAsString(user);
