JSON数据类型
数组用“[]”创建，对象用“{}”创建，并且使用Json基本都是用[]或者{}创建的数组或对象
fastjson 简介
fastjson是一个java语言编写的高性能且功能完善的JSON库，它采用一种“假定有序快速匹配”的算法，把JSON Parse 的性能提升到了极致。它的接口简单易用，已经被广泛使用在缓存序列化，协议交互，Web输出等各种应用场景中。
API
public static final Object parse(String text); // 把JSON文本parse为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为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); // 将JavaBean序列化为JSON文本
public static final String toJSONString(Object object, boolean prettyFormat); // 将JavaBean序列化为带格式的JSON文本
public static final Object toJSON(Object javaObject); //将JavaBean转换为JSONObject或者JSONArray。
使用方法举例
//将JSON文本转换为java对象
import com.alibaba.fastjson.JSON;
Model model = JSON.parseObject(jsonStr, Model.class);
fastjson 使用实例
/**
* User测试类
* @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 + "]";
}
}
import java.util.ArrayList;
import java.util.List;
/**
* 用户组测试类
* @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测试类
package demo;
import java.util.ArrayList;
import java.util.List;
import org.junit.Test;
import com.alibaba.fastjson.JSON;
/**
* fastJson测试类
* @author dmego
*
*/
public class TestFastJosn {
/**
* java对象转 json字符串
*/
@Test
public void objectTOJson(){
//简单java类转json字符串
User user = new User("dmego", "123456");
String UserJson = JSON.toJSONString(user);
System.out.println("简单java类转json字符串:"+UserJson);
//List<Object>转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>转json字符串:"+ListUserJson);
//复杂java类转json字符串
UserGroup userGroup = new UserGroup("userGroup", users);
String userGroupJson = JSON.toJSONString(userGroup);
System.out.println("复杂java类转json字符串:"+userGroupJson);
}
/**
* json字符串转java对象
* 注：字符串中使用双引号需要转义 (" --> \"),这里使用的是单引号
*/
@Test
public void JsonTOObject(){
/* json字符串转简单java对象
* 字符串：{"password":"123456","username":"dmego"}*/
String jsonStr1 = "{'password':'123456','username':'dmego'}";
User user = JSON.parseObject(jsonStr1, User.class);
System.out.println("json字符串转简单java对象:"+user.toString());
/*
* json字符串转List<Object>对象
* 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字符串转List<Object>对象:"+users.toString());
/*json字符串转复杂java对象
* 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字符串转复杂java对象:"+userGroup);
}
}
输出结果
简单java类转json字符串:{"password":"123456","username":"dmego"}
List<Object>转json字符串:[{"password":"123123","username":"zhangsan"},{"password":"321321","username":"lisi"}]
复杂java类转json字符串:{"name":"userGroup","users":[{"password":"123123","username":"zhangsan"},{"password":"321321","username":"lisi"}]}
json字符串转简单java对象:User [username=dmego, password=123456]
json字符串转List<Object>对象:[User [username=zhangsan, password=123123], User [username=lisi, password=321321]]
json字符串转复杂java对象:UserGroup [name=userGroup, users=[User [username=zhangsan, password=123123], User [username=lisi, password=321321]]]
fastjson 解析复杂嵌套json字符串
这个实例是我在开发中用到的，先给出要解析的json字符串
[
{
"id": "user_list",
"key": "id",
"tableName": "用户列表",
"className": "cn.dmego.domain.User",
"column": [
{
"key": "rowIndex",
"header": "序号",
"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": "序号",
"width": "50",
"allowSort": "false"
},
{
"key": "id",
"header": "id",
"hidden": "true"
},
{
"key": "name",
"header": "名称",
"width": "100",
"allowSort": "true"
}
]
}
]
要想解析这种复杂的字符串，首先得先定义好与之相符的java POJO 对象，经过观察，我们发现，这个是一个json对象数组，每一个对象里包含了许多属性，其中还有一个属性的类型也是对象数组。所有，我们从里到外，先定义最里面的对象：
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;
}
//这里省略部分getter与setter方法
}
再定义外层的对象：
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;
}
//这里省略部分getter与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;
}
}
我的这个json文件放置在类路径下，最后想将这个json字符串转化为List对象，并且将column 对象数组转化为query对象里的List属性
而实际转化过程中，fastjson将column对象数组转化为List;所有我们还需要将Map类型转化为object类型才能满足需求。
/**
* 读取类路径下的配置文件
* 解析成对象数组并返回
* @throws IOException
*/
@Test
public List<Query> test() throws IOException {
// 读取类路径下的query.json文件
ClassLoader cl = this.getClass().getClassLoader();
InputStream inputStream = cl.getResourceAsStream("query.json");
String jsontext = IOUtils.toString(inputStream, "utf8");
// 先将字符jie串转为List数组
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) {
//将map转化为java实体类
Column column = (Column)map2Object(linkedMap, Column.class);
System.out.println(column.toString());
columnList.add(column);
}
query.setColumnList(columnList); //为columnList属性赋值
}
return queryList;
}
/**
* Map转成实体对象
* @param map map实体对象包含属性
* @param clazz 实体对象类型
* @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;
}
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