Gson Fromjson () usage

1. Pure array JSON String conversions	[{"Name": "Zhangsan", "Age": "Ten", "Phone": "11111", "email": "[email protected]"}, {"Name": "Lisi", "Age": "a", "Phone": "22222", "email": "[email protected]"},   ... ] The parsing code is as follows: public class UserBean { //variable names must match JSON data field names private String name; Private String age; Private String phone; Private String Email; ... } Get the local JSON and turn it into a string String Strbyjson = Constructtestjsonstr ();//omission of function contents here Parsing class objects for JSON Jsonparser parser = new Jsonparser (); Converts a string of JSON into a Jsonarray object Jsonarray Jsonarray = Parser.parse (Strbyjson). Getasjsonarray (); Gson Gson = new Gson (); arraylist<userbean> userbeanlist = new arraylist<> (); Enhanced for Loop traversal Jsonarray for (Jsonelement User:jsonarray) { Use Gson to turn directly into bean objects UserBean UserBean = Gson.fromjson (user, userbean.class); Userbeanlist.add (UserBean); }
2. A pure array with data headers Data conversion	{"Muser": [{"Name": "Zhangsan", "Age": "Ten", "Phone": "11111", "email": "[email protected]"}, {"Name": "Lisi", "Age": "a", "Phone": "22222", "email": "[email protected]"}, ...] } Parsing a pure array with a data header Get the local JSON and turn it into a string String Strbyjson = Constructtestjsonstr ();//The contents of this function are omitted; Turn Jsonobject first. Jsonobject jsonobject = new Jsonparser (). Parse (Strbyjson). Getasjsonobject (); Re-Jsonarray plus data header Jsonarray Jsonarray = Jsonobject.getasjsonarray ("Muser"); Gson Gson = new Gson (); arraylist<userbean> userbeanlist = new arraylist<> (); Looping through for (Jsonelement User:jsonarray) { Get Userbean.class by Reflection UserBean UserBean = Gson.fromjson (user, new typetoken<userbean> () {}.gettype ()); Userbeanlist.add (UserBean); }
3. There is a complex data header Data conversion	"Code": $, "msg": "OK", "Muser": [{"Name": "Zhangsan", "Age": "Ten", "Phone": "11111", "email": "[email protected]"}, {"name": "Lisi", "Age": "a", "Phone": "22222", "email": "[email protected]"}, ...] } The parsed object is not a pure array of data, there are other fields + arrays (with headers), as follows: Build the bean based on JSON, note that the bean here is returning all fields, because Gson can parse directly into List, so the bean is the following, and also the get/set that occupy the place is omitted: public class Resultbean { //Note the variable name must be the same as the field name private int code; Private String msg; Private list<userbean> Muser; public class userbean{ private String name; Private String age; Private String phone; Private String Email; ... } ... } There is a general method of message head complex data as follows Get the JSON string String Strbyjson = Constructtestjsonstr ();//The contents of this function are omitted; Gson Direct parse into object Resultbean Resultbean = new Gson (). Fromjson (Strbyjson,resultbean.class); Get the collection in the object list<resultbean.userbean> userbeanlist = Resultbean.getmuser (); Three sentences to take care of, thus see Gson Strong
4. Parse only the complex JSON A portion of an array or array of contents	Data head Complex data interception method, such as the 3rd example of the JSON data content only want to take "Muser" array of age is more than 30 years old how to do? Method 1: Parse all, and then take from list. (But what if there were 10,000 data?) All parsing is too troublesome), Method 2: Conditional traversal! (The following code example): Parsing code: Get the JSON string String Strbyjson = Constructtestjsonstr ();//The contents of this function are omitted; list<userbean> userbeanlist = new arraylist<> (); Get the array Jsonobject jsonobject = new Jsonparser (). Parse (Strbyjson). Getasjsonobject (); Jsonarray Jsonarray = Jsonobject.getasjsonarray ("Muser"); Iterating through an array for (Jsonelement User:jsonarray) { UserBean UserBean = new Gson (). Fromjson (User, new typetoken<userbean> () { }.gettype ()); Filter by condition if (Integer.parseint (Userbean.getage ()) > 30) { Userbeanlist.add (UserBean); } }
5. Nesting Ultra-complex JSON Data conversion	Three ways: 1, all parse out; 2, what to parse what; 3,jsonreader, 1th/2 strokes explained above, the following example Jsonreader (similar to the node-wise interpretation of XML) Through the Jsonreader way to parse private void Parsecomplexjarraybyreader () throws IOException { String Strbyjson = Jsontostringutil.getstringbyjson (this, r.raw.juser_4); Jsonreader reader = new Jsonreader (new StringReader (Strbyjson)); try { Reader.beginobject (); String tagName = Reader.nextname (); if (Tagname.equals ("group")) { Read Group this node Readgroup (reader); } Reader.endobject (); } finally { Reader.close (); } } Read Group this node private void Readgroup (Jsonreader reader) throws IOException { Reader.beginobject (); while (Reader.hasnext ()) { String tagName = Reader.nextname (); if (tagname.equals ("user")) { Readuser (reader); } else if (tagname.equals ("info")) { Readinfo (reader); } } Reader.endobject (); } Read the user basic message the Users node private void Readuser (Jsonreader reader) throws IOException { Reader.beginobject (); while (Reader.hasnext ()) { String tag = Reader.nextname (); if (tag.equals ("name")) { String name = Reader.nextstring (); Nametext.settext (name); } else if (Tag.equals ("Age")) { String age = reader.nextstring (); Agetext.settext (age); } ... else { Reader.skipvalue ();//Ignore } } Reader.endobject (); } Read user other Messages Info node private void Readinfo (Jsonreader reader) throws IOException { Reader.beginobject (); while (Reader.hasnext ()) { String tag = Reader.nextname (); if (Tag.equals ("address")) { String address = reader.nextstring (); Addresstext.settext (address); } else if (Tag.equals ("work")) { String work = reader.nextstring (); Worktext.settext (work); } ... else { Reader.skipvalue ();//Ignore } } Reader.endobject (); }
6. Simple Data +list+map Transformation	public class Student { public int id; Public String nickname; public int age; public arraylist<string> Books; Public hashmap<string, string> Booksmap; } Student Student = new Student (); Student.id = 1; Student.nickname = "Jack"; Student.age = 22; Student.email = "[email protected]"; arraylist<string> books = new Arraylist<string> (); Books.add ("mathematics"); Books.add ("language"); Books.add ("English"); Books.add ("physical"); Books.add ("chemistry"); Books.add ("biology"); Student.books = books; hashmap<string, string> booksmap = new hashmap<string, string> (); Booksmap.put ("1", "mathematics"); Booksmap.put ("2", "language"); Booksmap.put ("3", "English"); Booksmap.put ("4", "Physical"); Booksmap.put ("5", "chemistry"); Booksmap.put ("6", "creature"); Student.booksmap = Booksmap; Gson Gson = new Gson (); String result = Gson.tojson (student); Student STUDENTG = Gson.fromjson (result, student.class); LOG.E ("Mainactivity", "ID:" + studentg.id); LOG.E ("Mainactivity", "nickname:" + Studentg.nickname); LOG.E ("Mainactivity", "Age:" + studentg.age); LOG.E ("mainactivity", "Email:" + studentg.email); LOG.E ("Mainactivity", "Books Size:" + studentG.books.size ()); LOG.E ("Mainactivity", "Booksmap Size:" + studentG.booksMap.size ()); Print output Id:1 Nickname:jack Age:22 Email:[email protected] Books Size:6 Booksmap Size:6
7. list or map etc. Collection The generics are replaced with a custom class	Generic definition Public hashmap<string,book> Booksmap; public class book{ public int id; public String name; } hashmap<string, book> booksmap = Gson.fromjson (result, new typetoken Gson Gson = new Gson (); hashmap<string, book> booksmap = new hashmap<> (); Booksmap.put ("Book1", new book (1, "Java Foundation Development")); Booksmap.put ("Book2", New book (2, "Java design mode")); Booksmap.put ("Book3", New book (3, "Java Algorithm")); String datastr = Gson.tojson (Booksmap); System.out.println ("Datastr:" + datastr); hashmap<string, book> booksMap2 = Gson.fromjson (datastr, New typetoken }.gettype ()); For (map.entry<string, book> entry:booksMap2.entrySet ()) { System.out.println ("Key:" +entry.getkey () + "value:" + entry.getvalue (). toString ()); } Output results datastr:{"Book2": {"id": 2, "name": "Java design mode"}, "Book1": {"id": 1, "name": "Java Basic Development"}, "Book3": {"id": 3, "name": "Java Algorithm" }} Key:book2 value:book{id=2, name= ' Java design mode '} Key:book1 value:book{id=1, Name= ' Java Foundation development '} Key:book3 value:book{id=3, name= ' Java algorithm '}

Gson Fromjson () usage