最近在開發過程當中使用了大量的json
做爲先後端數據交換的方式,因爲以前沒有對json
作過系統的學習,全部在使用過程當中查閱了大量的文檔與資料,這裏主要記錄了我在開發後對json
以及fastjson
使用的總結html
JSON
(javaScript Object Notation)是一種輕量級的數據交換格式。主要採用鍵值對({"name": "json"}
)的方式來保存和表示數據。JSON
是JS
對象的字符串表示法,它使用文本表示一個JS
對象的信息,本質上是一個字符串。更多簡介見介紹JSON。java
在日誌解析,先後端數據傳輸交互中,常常會遇到字符串(String)與json
,XML
等格式相互轉換與解析,其中json
以跨語言,跨先後端的優勢在開發中被頻繁使用,基本上能夠說是標準的數據交換格式。fastjson是一個java語言編寫的高性能且功能完善的JSON庫,它採用一種「假定有序快速匹配」的算法,把JSON Parse
的性能提高到了極致。它的接口簡單易用,已經被普遍使用在緩存序列化,協議交互,Web輸出等各類應用場景中。git
fastjson API 入口類是com.alibaba.fastjson.JSON
,經常使用的序列化操做均可以在JSON
類上的靜態方法直接完成。github
public static final Object parse(String text); // 把JSON文本parse爲JSONObject或者JSONArray public static final JSONObject parseObject(String text); // 把JSON文本parse成JSONObject public static final <T> T parseObject(String text, Class<T> clazz); // 把JSON文本parse爲JavaBean public static final JSONArray parseArray(String text); // 把JSON文本parse成JSONArray public static final <T> List<T> parseArray(String text, Class<T> clazz); //把JSON文本parse成JavaBean集合 public static final String toJSONString(Object object); // 將JavaBean序列化爲JSON文本 public static final String toJSONString(Object object, boolean prettyFormat); // 將JavaBean序列化爲帶格式的JSON文本 public static final Object toJSON(Object javaObject); //將JavaBean轉換爲JSONObject或者JSONArray。
//將JSON文本轉換爲java對象 import com.alibaba.fastjson.JSON; Model model = JSON.parseObject(jsonStr, Model.class);
User測試類算法
/** * User測試類 * @author dmego */ public class User { private String username; private String password; public User(){} public User(String username,String password){ this.username = username; this.password = password; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override public String toString() { return "User [username=" + username + ", password=" + password + "]"; } }
UserGroup測試類apache
import java.util.ArrayList; import java.util.List; /** * 用戶組測試類 * @author dmego * */ public class UserGroup { private String name; private List<User> users = new ArrayList<User>(); public UserGroup(){} public UserGroup(String name,List<User> users){ this.name = name; this.users = users; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<User> getUsers() { return users; } public void setUsers(List<User> users) { this.users = users; } @Override public String toString() { return "UserGroup [name=" + name + ", users=" + users + "]"; } }
fastJson測試類json
package demo; import java.util.ArrayList; import java.util.List; import org.junit.Test; import com.alibaba.fastjson.JSON; /** * fastJson測試類 * @author dmego * */ public class TestFastJosn { /** * java對象轉 json字符串 */ @Test public void objectTOJson(){ //簡單java類轉json字符串 User user = new User("dmego", "123456"); String UserJson = JSON.toJSONString(user); System.out.println("簡單java類轉json字符串:"+UserJson); //List<Object>轉json字符串 User user1 = new User("zhangsan", "123123"); User user2 = new User("lisi", "321321"); List<User> users = new ArrayList<User>(); users.add(user1); users.add(user2); String ListUserJson = JSON.toJSONString(users); System.out.println("List<Object>轉json字符串:"+ListUserJson); //複雜java類轉json字符串 UserGroup userGroup = new UserGroup("userGroup", users); String userGroupJson = JSON.toJSONString(userGroup); System.out.println("複雜java類轉json字符串:"+userGroupJson); } /** * json字符串轉java對象 * 注:字符串中使用雙引號須要轉義 (" --> \"),這裏使用的是單引號 */ @Test public void JsonTOObject(){ /* json字符串轉簡單java對象 * 字符串:{"password":"123456","username":"dmego"}*/ String jsonStr1 = "{'password':'123456','username':'dmego'}"; User user = JSON.parseObject(jsonStr1, User.class); System.out.println("json字符串轉簡單java對象:"+user.toString()); /* * json字符串轉List<Object>對象 * 字符串:[{"password":"123123","username":"zhangsan"},{"password":"321321","username":"lisi"}] */ String jsonStr2 = "[{'password':'123123','username':'zhangsan'},{'password':'321321','username':'lisi'}]"; List<User> users = JSON.parseArray(jsonStr2, User.class); System.out.println("json字符串轉List<Object>對象:"+users.toString()); /*json字符串轉複雜java對象 * 字符串:{"name":"userGroup","users":[{"password":"123123","username":"zhangsan"},{"password":"321321","username":"lisi"}]} * */ String jsonStr3 = "{'name':'userGroup','users':[{'password':'123123','username':'zhangsan'},{'password':'321321','username':'lisi'}]}"; UserGroup userGroup = JSON.parseObject(jsonStr3, UserGroup.class); System.out.println("json字符串轉複雜java對象:"+userGroup); } }
輸出結果後端
簡單java類轉json字符串:{"password":"123456","username":"dmego"} List<Object>轉json字符串:[{"password":"123123","username":"zhangsan"},{"password":"321321","username":"lisi"}] 複雜java類轉json字符串:{"name":"userGroup","users":[{"password":"123123","username":"zhangsan"},{"password":"321321","username":"lisi"}]} json字符串轉簡單java對象:User [username=dmego, password=123456] json字符串轉List<Object>對象:[User [username=zhangsan, password=123123], User [username=lisi, password=321321]] json字符串轉複雜java對象:UserGroup [name=userGroup, users=[User [username=zhangsan, password=123123], User [username=lisi, password=321321]]]
這個實例是我在開發中用到的,先給出要解析的json字符串數組
[ { "id": "user_list", "key": "id", "tableName": "用戶列表", "className": "cn.dmego.domain.User", "column": [ { "key": "rowIndex", "header": "序號", "width": "50", "allowSort": "false" }, { "key": "id", "header": "id", "hidden": "true" }, { "key": "name", "header": "姓名", "width": "100", "allowSort": "true" } ] }, { "id": "role_list", "key": "id", "tableName": "角色列表", "className": "cn.dmego.domain.Role", "column": [ { "key": "rowIndex", "header": "序號", "width": "50", "allowSort": "false" }, { "key": "id", "header": "id", "hidden": "true" }, { "key": "name", "header": "名稱", "width": "100", "allowSort": "true" } ] } ]
要想解析這種複雜的字符串,首先得先定義好與之相符的java POJO 對象,通過觀察,咱們發現,這個是一個json對象數組,每個對象裏包含了許多屬性,其中還有一個屬性的類型也是對象數組。全部,咱們從裏到外,先定義最裏面的對象:緩存
public class Column { private String key; private String header; private String width; private String allowSort; private String hidden; public String getKey() { return key; } public void setKey(String key) { this.key = key; } //這裏省略部分getter與setter方法 }
再定義外層的對象:
import java.util.List; import org.apache.commons.collections4.map.LinkedMap; public class Query { private String id; private String key; private String tableName; private String className; private List<LinkedMap<String, Object>> column; private List<Column> columnList; public String getId() { return id; } public void setId(String id) { this.id = id; } //這裏省略部分getter與setter方法 public List<LinkedMap<String, Object>> getColumn() { return column; } public void setColumn(List<LinkedMap<String, Object>> column) { this.column = column; } public List<Column> getColumnList() { return columnList; } public void setColumnList(List<Column> columnList) { this.columnList = columnList; } }
個人這個json文件放置在類路徑下,最後想將這個json字符串轉化爲List<Query>對象,而且將column 對象數組轉化爲query對象裏的List<Column>屬性
而實際轉化過程當中,fastjson將column對象數組轉化爲List<Map>;全部咱們還須要將Map類型轉化爲object類型才能知足需求。
/** * 讀取類路徑下的配置文件 * 解析成對象數組並返回 * @throws IOException */ @Test public List<Query> test() throws IOException { // 讀取類路徑下的query.json文件 ClassLoader cl = this.getClass().getClassLoader(); InputStream inputStream = cl.getResourceAsStream("query.json"); String jsontext = IOUtils.toString(inputStream, "utf8"); // 先將字符jie串轉爲List數組 List<Query> queryList = JSON.parseArray(jsontext, Query.class); for (Query query : queryList) { List<Column> columnList = new ArrayList<Column>(); List<LinkedMap<String,Object>> columns = query.getColumn(); for (LinkedMap<String, Object> linkedMap : columns) { //將map轉化爲java實體類 Column column = (Column)map2Object(linkedMap, Column.class); System.out.println(column.toString()); columnList.add(column); } query.setColumnList(columnList); //爲columnList屬性賦值 } return queryList; } /** * Map轉成實體對象 * @param map map實體對象包含屬性 * @param clazz 實體對象類型 * @return */ public static Object map2Object(Map<String, Object> map, Class<?> clazz) { if (map == null) { return null; } Object obj = null; try { obj = clazz.newInstance(); Field[] fields = obj.getClass().getDeclaredFields(); for (Field field : fields) { int mod = field.getModifiers(); if (Modifier.isStatic(mod) || Modifier.isFinal(mod)) { continue; } field.setAccessible(true); String flag = (String) map.get(field.getName()); if(flag != null){ if(flag.equals("false") || flag.equals("true")){ field.set(obj, Boolean.parseBoolean(flag)); }else{ field.set(obj, map.get(field.getName())); } } } } catch (Exception e) { e.printStackTrace(); } return obj; }