版權聲明：本文為博主原創文章，未經博主同意不得轉載。 https://blog.csdn.net/jadyer/article/details/24395015

完整版見https://jadyer.github.io/

先列出來正確的解析代碼，接著再描寫敘述問題詳情。

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;} }
以下是生成json和解析json的代碼

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":"網絡文學"},"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("網絡文學"); // 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\":\"網絡文學\"},\"name\":\"玄玉\"}";//用到的jar為fastjson-1.1.36.jarUser 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為jackson-all-1.9.11.jarUser userFromJackson = new ObjectMapper().readValue(jsonText, User.class);System.out.println(ReflectionToStringBuilder.toString(userFromJackson.getBook().getAuthor(), ToStringStyle.MULTI_LINE_STYLE));} }
接下來描寫敘述下遇到的問題

//上面解析正常時用到的json串 //"{\"book\":{\"author\":{\"money\":500,\"name\":\"南派三叔\"},\"name\":\"網絡文學\"},\"name\":\"玄玉\"}"; //我在用fastjson和jackson解析時都會報錯時用的json串 //"{\"book\":{\"author\":[{\"money\":500,\"name\":\"南派三叔\"}],\"name\":\"網絡文學\"},\"name\":\"玄玉\"}"; //它倆的差別在于:book中僅僅有一個author對象,僅僅是多加了[],但其仍為合法的json串 //而且http://tool.oschina.net/codeformat/json均驗證通過
但在解析時。FastJSON會報以下的異常

Exception in thread "main" com.alibaba.fastjson.JSONException: syntax error, expect {, actual ], pos 39at 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會報以下的異常

Exception in thread "main" org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of com.jadyer.model.Author out of START_ARRAY tokenat [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)
個人感覺Jackson的異常看上去更直觀，可能是二者內部的驗證邏輯不同導致的

只是還是傾向于FastJSON，即便一時之間沒看明確它的異常描寫敘述。但那也僅僅是這方面的經驗不足而已

以下說一下解決的方法：Book.java中將author改動為List<Author>類型的屬性。并加入相應的setter和getter就可以

個人的理解是：FastJSON和Jackson解析json為JavaBean時，先查看實體類的相應屬性

當發現該屬性不能承載多個對象值，且json串中恰好該屬性使用的是中括號。這并非它預期的大括號，于是報錯了

轉載于:https://www.cnblogs.com/ldxsuanfa/p/10034445.html

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