先列出来正确的解析代码，接着再描述问题详情。
首先是用到的JavaBean
package com.jadyer.model;
public class User {
private String name;
private Book book;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Book getBook() {
return book;
}
public void setBook(Book book) {
this.book = book;
}
}
package com.jadyer.model;
public class Book {
private String name;
// private List<Author> author = new ArrayList<Author>();
private Author author;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
// public List<Author> getAuthor() {
// return author;
// }
// public void setAuthor(List<Author> author) {
// this.author = author;
// }
public Author getAuthor() {
return author;
}
public void setAuthor(Author author) {
this.author = author;
}
}
package com.jadyer.model;
public class Author {
private String name;
private int money;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getMoney() {
return money;
}
public void setMoney(int money) {
this.money = money;
}
}
下面是生成json和解析json的代码
package com.jadyer.main;
import java.io.IOException;
import org.apache.commons.lang3.builder.ReflectionToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import com.alibaba.fastjson.JSON;
import com.jadyer.model.User;
public class JSONDemo {
// /**
// * 生成{"book":{"author":[{"money":500,"name":"南派三叔"},{"money":200,"name":"孔二狗"}],"name":"网络文学"},"name":"玄玉"}
// */
// private static String format(){
// List<Author> authorList = new ArrayList<Author>();
// Author author11 = new Author();
// author11.setName("南派三叔");
// author11.setMoney(500);
// authorList.add(author11);
// Author author22 = new Author();
// author22.setName("孔二狗");
// author22.setMoney(200);
// authorList.add(author22);
// Book book = new Book();
// book.setName("网络文学");
// book.setAuthor(authorList);
// User user = new User();
// user.setName("玄玉");
// user.setBook(book);
// return JSON.toJSONString(user);
// }
public static void main(String[] args) throws JsonParseException,JsonMappingException,IOException {
String jsonText = "{\"book\":{\"author\":{\"money\":500,\"name\":\"南派三叔\"},\"name\":\"网络文学\"},\"name\":\"玄玉\"}";
//用到的jar为fastjson-1.1.36.jar
User userFromFastJSON = JSON.parSEObject(jsonText,User.class);
System.out.println(ReflectionToStringBuilder.toString(userFromFastJSON.getBook().getAuthor(),ToStringStyle.MULTI_LINE_STYLE));
System.out.println("----------------------------------------------------------------------------------");
//用到的jar为jackson-all-1.9.11.jar
User userFromJackson = new ObjectMapper().readValue(jsonText,User.class);
System.out.println(ReflectionToStringBuilder.toString(userFromJackson.getBook().getAuthor(),ToStringStyle.MULTI_LINE_STYLE));
}
}
接下来描述下遇到的问题
//上面解析正常时用到的json串
//"{\"book\":{\"author\":{\"money\":500,\"name\":\"玄玉\"}";
//我在用fastjson和jackson解析时都会报错时用的json串
//"{\"book\":{\"author\":[{\"money\":500,\"name\":\"南派三叔\"}],\"name\":\"玄玉\"}";
//它俩的区别在于:book中只有一个author对象,只是多加了[],但其仍为合法的json串
//并且http://tool.oschina.net/codeformat/json均验证通过
但在解析时，FastJSON会报下面的异常
Exception in thread "main" com.alibaba.fastjson.JSONException: Syntax error,expect {,actual ],pos 39 at com.alibaba.fastjson.parser.deserializer.JavaBeanDeserializer.deserialze(JavaBeanDeserializer.java:212) at com.alibaba.fastjson.parser.deserializer.ASMJavaBeanDeserializer.parseRest(ASMJavaBeanDeserializer.java:96) at Fastjson_ASM_User_1.deserialze(Unknown Source) at com.alibaba.fastjson.parser.DefaultJSONParser.parSEObject(DefaultJSONParser.java:513) at com.alibaba.fastjson.JSON.parSEObject(JSON.java:244) at com.alibaba.fastjson.JSON.parSEObject(JSON.java:220) at com.alibaba.fastjson.JSON.parSEObject(JSON.java:179) at com.alibaba.fastjson.JSON.parSEObject(JSON.java:323) at com.jadyer.main.JSONDemoDetail.main(JSONDemoDetail.java:18)
Jackson会报下面的异常
Exception in thread "main" org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of com.jadyer.model.Author out of START_ARRAY token at [Source: java.io.StringReader@509ced8e; line: 1,column: 10] (through reference chain: com.jadyer.model.User["book"]->com.jadyer.model.Book["author"]) at org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:163) at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:219) at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:212) at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromArray(BeanDeserializer.java:875) at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:597) at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:299) at org.codehaus.jackson.map.deser.SettableBeanProperty$MethodProperty.deserializeAndSet(SettableBeanProperty.java:414) at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:697) at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580) at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:299) at org.codehaus.jackson.map.deser.SettableBeanProperty$MethodProperty.deserializeAndSet(SettableBeanProperty.java:414) at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:697) at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580) at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2732) at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1863) at com.jadyer.main.JSONDemoDetail.main(JSONDemoDetail.java:22)
个人感觉Jackson的异常看上去更直观，可能是二者内部的验证逻辑不同导致的
不过还是倾向于FastJSON，即便一时之间没看明白它的异常描述，但那也只是这方面的经验不足而已
下面说一下解决办法：Book.java中将author修改为List<Author>类型的属性，并添加对应的setter和getter即可
个人的理解是：FastJSON和Jackson解析json为JavaBean时，先查看实体类的对应属性
原文链接：https://www.f2er.com/json/290215.html