我是靠谱客的博主 专一水池，最近开发中收集的这篇文章主要介绍com.alibaba.fastjson.JSONException: syntax error, expect {, actual [, pos 99, fieldName，觉得挺不错的，现在分享给大家，希望可以做个参考。
概述
转载自：https://blog.csdn.net/jadyer/article/details/24395015
完整版见https://jadyer.github.io/
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
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package com.jadyer.model;
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public
class User {
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private String name;
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private Book book;
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public Book getBook() {
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return book;
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}
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public void setBook(Book book) {
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this.book = book;
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}
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}
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package com.jadyer.model;
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public
class Book {
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private String name;
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// private List<Author> author = new ArrayList<Author>();
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private Author author;
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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// public List<Author> getAuthor() {
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// return author;
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// }
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// public void setAuthor(List<Author> author) {
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// this.author = author;
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// }
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public Author getAuthor() {
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return author;
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}
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public void setAuthor(Author author) {
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this.author = author;
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}
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}
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package com.jadyer.model;
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public
class Author {
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private String name;
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private
int money;
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public int getMoney() {
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return money;
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}
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public void setMoney(int money) {
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this.money = money;
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}
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}
下面是生成json和解析json的代码
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package com.jadyer.main;
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import java.io.IOException;
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import org.apache.commons.lang3.builder.ReflectionToStringBuilder;
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import org.apache.commons.lang3.builder.ToStringStyle;
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import org.codehaus.jackson.JsonParseException;
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import org.codehaus.jackson.map.JsonMappingException;
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import org.codehaus.jackson.map.ObjectMapper;
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import com.alibaba.fastjson.JSON;
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import com.jadyer.model.User;
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public
class JSONDemo {
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// /**
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// * 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"}
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// */
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// private static String format(){
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// List<Author> authorList = new ArrayList<Author>();
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// Author author11 = new Author();
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// author11.setName("南派三叔");
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// author11.setMoney(500);
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// authorList.add(author11);
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// Author author22 = new Author();
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// author22.setName("孔二狗");
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// author22.setMoney(200);
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// authorList.add(author22);
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// Book book = new Book();
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// book.setName("网络文学");
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// book.setAuthor(authorList);
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// User user = new User();
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// user.setName("玄玉");
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// user.setBook(book);
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// return JSON.toJSONString(user);
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// }
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public static void main(String[] args) throws JsonParseException, JsonMappingException, IOException {
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String jsonText =
"{"book":{"author":{"money":500,"name":"南派三叔"},"name":"网络文学"},"name":"玄玉"}";
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//用到的jar为fastjson-1.1.36.jar
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User userFromFastJSON = JSON.parseObject(jsonText, User.class);
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System.out.println(ReflectionToStringBuilder.toString(userFromFastJSON.getBook().getAuthor(), ToStringStyle.MULTI_LINE_STYLE));
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System.out.println(
"----------------------------------------------------------------------------------");
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//用到的jar为jackson-all-1.9.11.jar
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User userFromJackson =
new ObjectMapper().readValue(jsonText, User.class);
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System.out.println(ReflectionToStringBuilder.toString(userFromJackson.getBook().getAuthor(), ToStringStyle.MULTI_LINE_STYLE));
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}
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}
接下来描述下遇到的问题
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//上面解析正常时用到的json串
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//"{"book":{"author":{"money":500,"name":"南派三叔"},"name":"网络文学"},"name":"玄玉"}";
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//我在用fastjson和jackson解析时都会报错时用的json串
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//"{"book":{"author":[{"money":500,"name":"南派三叔"}],"name":"网络文学"},"name":"玄玉"}";
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//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
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//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
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Exception in thread
"main" com.alibaba.fastjson.JSONException: syntax error, expect {, actual ], pos
39
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at com.alibaba.fastjson.parser.deserializer.JavaBeanDeserializer.deserialze(JavaBeanDeserializer.java:
212)
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at com.alibaba.fastjson.parser.deserializer.ASMJavaBeanDeserializer.parseRest(ASMJavaBeanDeserializer.java:
96)
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at Fastjson_ASM_User_1.deserialze(Unknown Source)
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at com.alibaba.fastjson.parser.DefaultJSONParser.parseObject(DefaultJSONParser.java:
513)
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at com.alibaba.fastjson.JSON.parseObject(JSON.java:
244)
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at com.alibaba.fastjson.JSON.parseObject(JSON.java:
220)
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at com.alibaba.fastjson.JSON.parseObject(JSON.java:
179)
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at com.alibaba.fastjson.JSON.parseObject(JSON.java:
323)
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at com.jadyer.main.JSONDemoDetail.main(JSONDemoDetail.java:
18)
Jackson会报下面的异常
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Exception in thread
"main" org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of com.jadyer.model.Author out of START_ARRAY token
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at [Source: java.io.StringReader@
509ced8e; line:
1, column:
10] (through reference chain: com.jadyer.model.User[
"book"]->com.jadyer.model.Book[
"author"])
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at org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:
163)
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at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:
219)
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at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:
212)
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at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromArray(BeanDeserializer.java:
875)
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at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:
597)
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at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:
299)
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at org.codehaus.jackson.map.deser.SettableBeanProperty$MethodProperty.deserializeAndSet(SettableBeanProperty.java:
414)
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at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:
697)
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at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:
580)
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at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:
299)
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at org.codehaus.jackson.map.deser.SettableBeanProperty$MethodProperty.deserializeAndSet(SettableBeanProperty.java:
414)
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at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:
697)
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at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:
580)
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at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:
2732)
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at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:
1863)
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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
当发现该属性不能承载多个对象值，且json串中恰好该属性使用的是中括号，这并不是它预期的大括号，于是报错了
最后
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