我有以下JSON文本。我如何解析它以获得pageName, pagePic, post_id等的值?
{
"pageInfo": {
"pageName": "abc",
"pagePic": "http://example.com/content.jpg"
},
"posts": [
{
"post_id": "123456789012_123456789012",
"actor_id": "1234567890",
"picOfPersonWhoPosted": "http://example.com/photo.jpg",
"nameOfPersonWhoPosted": "Jane Doe",
"message": "Sounds cool. Can't wait to see it!",
"likesCount": "2",
"comments": [],
"timeOfPost": "1234567890"
}
]
}
当前回答
任何类型的json数组 解决问题的步骤。
将JSON对象转换为java对象。 你可以使用这个链接或任何在线工具。 保存为java类，如Myclass.java。 Myclass obj = new Gson().fromJson(JsonStr, Myclass.class); 使用obj，你可以得到你的值。
其他回答
除了其他答案，我推荐这个在线开源服务jsonschema2pojo.org，它可以从json或json模式快速生成Java类，用于GSON, Jackson 1。或者Jackson 2.x。例如，如果你有:
{
"pageInfo": {
"pageName": "abc",
"pagePic": "http://example.com/content.jpg"
}
"posts": [
{
"post_id": "123456789012_123456789012",
"actor_id": 1234567890,
"picOfPersonWhoPosted": "http://example.com/photo.jpg",
"nameOfPersonWhoPosted": "Jane Doe",
"message": "Sounds cool. Can't wait to see it!",
"likesCount": 2,
"comments": [],
"timeOfPost": 1234567890
}
]
}
GSON的jsonschema2pojo.org生成:
@Generated("org.jsonschema2pojo")
public class Container {
@SerializedName("pageInfo")
@Expose
public PageInfo pageInfo;
@SerializedName("posts")
@Expose
public List<Post> posts = new ArrayList<Post>();
}
@Generated("org.jsonschema2pojo")
public class PageInfo {
@SerializedName("pageName")
@Expose
public String pageName;
@SerializedName("pagePic")
@Expose
public String pagePic;
}
@Generated("org.jsonschema2pojo")
public class Post {
@SerializedName("post_id")
@Expose
public String postId;
@SerializedName("actor_id")
@Expose
public long actorId;
@SerializedName("picOfPersonWhoPosted")
@Expose
public String picOfPersonWhoPosted;
@SerializedName("nameOfPersonWhoPosted")
@Expose
public String nameOfPersonWhoPosted;
@SerializedName("message")
@Expose
public String message;
@SerializedName("likesCount")
@Expose
public long likesCount;
@SerializedName("comments")
@Expose
public List<Object> comments = new ArrayList<Object>();
@SerializedName("timeOfPost")
@Expose
public long timeOfPost;
}
如果你的数据很简单，你不想要外部依赖，可以使用以下几行代码:
/**
* A very simple JSON parser for one level, everything quoted.
* @param json the json content.
* @return a key => value map.
*/
public static Map<String, String> simpleParseJson(String json) {
Map<String, String> map = new TreeMap<>();
String qs[] = json.replace("\\\"", "\u0001").replace("\\\\", "\\").split("\"");
for (int i = 1; i + 3 < qs.length; i += 4) {
map.put(qs[i].replace('\u0001', '"'), qs[i + 2].replace('\u0001', '"'));
}
return map;
}
这些数据
{"name":"John", "age":"30", "car":"a \"quoted\" back\\slash car"}
生成一个包含
{age=30, car=a "quoted" back\slash car, name=John}
这也可以升级为使用未加引号的值…
/**
* A very simple JSON parser for one level, names are quoted.
* @param json the json content.
* @return a key => value map.
*/
public static Map<String, String> simpleParseJson(String json) {
Map<String, String> map = new TreeMap<>();
String qs[] = json.replace("\\\"", "\u0001").replace("\\\\", "\\").split("\"");
for (int i = 1; i + 1 < qs.length; i += 4) {
if (qs[i + 1].trim().length() > 1) {
String x = qs[i + 1].trim();
map.put(qs[i].replace('\u0001', '"'), x.substring(1, x.length() - 1).trim().replace('\u0001', '"'));
i -= 2;
} else {
map.put(qs[i].replace('\u0001', '"'), qs[i + 2].replace('\u0001', '"'));
}
}
return map;
}
为了解决复杂的结构，它变得很难看… ．.． 对不起! !．.． 但我忍不住把它编码了^^ 这将解析给定的JSON以及更多内容。它产生嵌套的映射和列表。
/**
* A very simple JSON parser, names are quoted.
*
* @param json the json content.
* @return a key => value map.
*/
public static Map<String, Object> simpleParseJson(String json) {
Map<String, Object> map = new TreeMap<>();
String qs[] = json.replace("\\\"", "\u0001").replace("\\\\", "\\").split("\"");
int index[] = { 1 };
recurse(index, map, qs);
return map;
}
/**
* Eierlegende Wollmilchsau.
*
* @param index index into array.
* @param map the current map to fill.
* @param qs the data.
*/
private static void recurse(int[] index, Map<String, Object> map, String[] qs) {
int i = index[0];
for (;; i += 4) {
String end = qs[i - 1].trim(); // check for termination of an object
if (end.startsWith("}")) {
qs[i - 1] = end.substring(1).trim();
i -= 4;
break;
}
String key = qs[i].replace('\u0001', '"');
String x = qs[i + 1].trim();
if (x.endsWith("{")) {
x = x.substring(0, x.length() - 1).trim();
if (x.endsWith("[")) {
List<Object> list = new ArrayList<>();
index[0] = i + 2;
for (;;) {
Map<String, Object> inner = new TreeMap<>();
list.add(inner);
recurse(index, inner, qs);
map.put(key, list);
i = index[0];
String y = qs[i + 3]; // check for termination of array
if (y.startsWith("]")) {
qs[i + 3] = y.substring(1).trim();
break;
}
}
continue;
}
Map<String, Object> inner = new TreeMap<>();
index[0] = i + 2;
recurse(index, inner, qs);
map.put(key, inner);
i = index[0];
continue;
}
if (x.length() > 1) { // unquoted
String value = x.substring(1, x.length() - 1).trim().replace('\u0001', '"');
if ("[]".equals(value)) // handle empty array
map.put(key, new ArrayList<>());
else
map.put(key, value);
i -= 2;
} else {
map.put(key, qs[i + 2].replace('\u0001', '"'));
}
}
index[0] = i;
}
yield -如果你打印地图:
{pageInfo={pageName=abc, pagePic=http://example.com/content.jpg}, posts=[{actor_id=1234567890, comments=[], likesCount=2, message=Sounds cool. Can't wait to see it!, nameOfPersonWhoPosted=Jane Doe, picOfPersonWhoPosted=http://example.com/photo.jpg, post_id=123456789012_123456789012, timeOfPost=1234567890}]}
Quick-json解析器非常简单，灵活，快速，可定制。试一试
特点:
Compliant with JSON specification (RFC4627) High-Performance JSON parser Supports Flexible/Configurable parsing approach Configurable validation of key/value pairs of any JSON Hierarchy Easy to use # Very small footprint Raises developer friendly and easy to trace exceptions Pluggable Custom Validation support - Keys/Values can be validated by configuring custom validators as and when encountered Validating and Non-Validating parser support Support for two types of configuration (JSON/XML) for using quick-JSON validating parser Requires JDK 1.5 No dependency on external libraries Support for JSON Generation through object serialisation Support for collection type selection during parsing process
它可以这样使用:
JsonParserFactory factory=JsonParserFactory.getInstance();
JSONParser parser=factory.newJsonParser();
Map jsonMap=parser.parseJson(jsonString);
A -解释
您可以使用Jackson库，将JSON字符串绑定到POJO(普通旧Java对象)实例中。POJO只是一个只有私有字段和公共getter/setter方法的类。Jackson将遍历这些方法(使用反射)，并将JSON对象映射到POJO实例，因为类的字段名与JSON对象的字段名相匹配。
在JSON对象中，它实际上是一个复合对象，主对象由两个子对象组成。因此，我们的POJO类应该具有相同的层次结构。我将把整个JSON对象称为Page对象。Page对象由PageInfo对象和Post对象数组组成。
所以我们必须创建三个不同的POJO类;
页面类，PageInfo类和Post实例数组的组合 PageInfo类 文章类
我唯一用过的包是Jackson ObjectMapper，我们做的是绑定数据;
com.fasterxml.jackson.databind.ObjectMapper
所需的依赖项，jar文件如下所示;
jackson-core-2.5.1.jar jackson-databind-2.5.1.jar jackson-annotations-2.5.0.jar
这里是所需的代码;
主POJO类:页
package com.levo.jsonex.model;
public class Page {
private PageInfo pageInfo;
private Post[] posts;
public PageInfo getPageInfo() {
return pageInfo;
}
public void setPageInfo(PageInfo pageInfo) {
this.pageInfo = pageInfo;
}
public Post[] getPosts() {
return posts;
}
public void setPosts(Post[] posts) {
this.posts = posts;
}
}
C -儿童POJO类:PageInfo
package com.levo.jsonex.model;
public class PageInfo {
private String pageName;
private String pagePic;
public String getPageName() {
return pageName;
}
public void setPageName(String pageName) {
this.pageName = pageName;
}
public String getPagePic() {
return pagePic;
}
public void setPagePic(String pagePic) {
this.pagePic = pagePic;
}
}
D -儿童POJO类:Post
package com.levo.jsonex.model;
public class Post {
private String post_id;
private String actor_id;
private String picOfPersonWhoPosted;
private String nameOfPersonWhoPosted;
private String message;
private int likesCount;
private String[] comments;
private int timeOfPost;
public String getPost_id() {
return post_id;
}
public void setPost_id(String post_id) {
this.post_id = post_id;
}
public String getActor_id() {
return actor_id;
}
public void setActor_id(String actor_id) {
this.actor_id = actor_id;
}
public String getPicOfPersonWhoPosted() {
return picOfPersonWhoPosted;
}
public void setPicOfPersonWhoPosted(String picOfPersonWhoPosted) {
this.picOfPersonWhoPosted = picOfPersonWhoPosted;
}
public String getNameOfPersonWhoPosted() {
return nameOfPersonWhoPosted;
}
public void setNameOfPersonWhoPosted(String nameOfPersonWhoPosted) {
this.nameOfPersonWhoPosted = nameOfPersonWhoPosted;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public int getLikesCount() {
return likesCount;
}
public void setLikesCount(int likesCount) {
this.likesCount = likesCount;
}
public String[] getComments() {
return comments;
}
public void setComments(String[] comments) {
this.comments = comments;
}
public int getTimeOfPost() {
return timeOfPost;
}
public void setTimeOfPost(int timeOfPost) {
this.timeOfPost = timeOfPost;
}
}
E -样本JSON文件:sampleJSONFile.json
我刚刚将JSON示例复制到这个文件中，并将其放在项目文件夹下。
{
"pageInfo": {
"pageName": "abc",
"pagePic": "http://example.com/content.jpg"
},
"posts": [
{
"post_id": "123456789012_123456789012",
"actor_id": "1234567890",
"picOfPersonWhoPosted": "http://example.com/photo.jpg",
"nameOfPersonWhoPosted": "Jane Doe",
"message": "Sounds cool. Can't wait to see it!",
"likesCount": "2",
"comments": [],
"timeOfPost": "1234567890"
}
]
}
F -演示代码
package com.levo.jsonex;
import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.levo.jsonex.model.Page;
import com.levo.jsonex.model.PageInfo;
import com.levo.jsonex.model.Post;
public class JSONDemo {
public static void main(String[] args) {
ObjectMapper objectMapper = new ObjectMapper();
try {
Page page = objectMapper.readValue(new File("sampleJSONFile.json"), Page.class);
printParsedObject(page);
} catch (IOException e) {
e.printStackTrace();
}
}
private static void printParsedObject(Page page) {
printPageInfo(page.getPageInfo());
System.out.println();
printPosts(page.getPosts());
}
private static void printPageInfo(PageInfo pageInfo) {
System.out.println("Page Info;");
System.out.println("**********");
System.out.println("\tPage Name : " + pageInfo.getPageName());
System.out.println("\tPage Pic : " + pageInfo.getPagePic());
}
private static void printPosts(Post[] posts) {
System.out.println("Page Posts;");
System.out.println("**********");
for(Post post : posts) {
printPost(post);
}
}
private static void printPost(Post post) {
System.out.println("\tPost Id : " + post.getPost_id());
System.out.println("\tActor Id : " + post.getActor_id());
System.out.println("\tPic Of Person Who Posted : " + post.getPicOfPersonWhoPosted());
System.out.println("\tName Of Person Who Posted : " + post.getNameOfPersonWhoPosted());
System.out.println("\tMessage : " + post.getMessage());
System.out.println("\tLikes Count : " + post.getLikesCount());
System.out.println("\tComments : " + Arrays.toString(post.getComments()));
System.out.println("\tTime Of Post : " + post.getTimeOfPost());
}
}
G -演示输出
Page Info;
****(*****
Page Name : abc
Page Pic : http://example.com/content.jpg
Page Posts;
**********
Post Id : 123456789012_123456789012
Actor Id : 1234567890
Pic Of Person Who Posted : http://example.com/photo.jpg
Name Of Person Who Posted : Jane Doe
Message : Sounds cool. Can't wait to see it!
Likes Count : 2
Comments : []
Time Of Post : 1234567890
Gson很容易学习和实现，我们需要知道的是以下两种方法
toJson() -将Java对象转换为JSON格式 fromJson() -将JSON转换为Java对象
`
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import com.google.gson.Gson;
public class GsonExample {
public static void main(String[] args) {
Gson gson = new Gson();
try {
BufferedReader br = new BufferedReader(
new FileReader("c:\\file.json"));
//convert the json string back to object
DataObject obj = gson.fromJson(br, DataObject.class);
System.out.println(obj);
} catch (IOException e) {
e.printStackTrace();
}
}
}
`
