java封装json串示例

Welcome to the Java JSON Example Tutorial. JSON (JavaScript Object Notation) is text-based lightweight technology for generating human readable formatted data. JSON represent object data in the form of key-value pairs. We can have nested JSON objects too and it provides an easy way to represent arrays also.

欢迎使用Java JSON示例教程。 JSON （JavaScript对象表示法）是一种基于文本的轻量级技术，用于生成人类可读的格式化数据。 JSON以键值对的形式表示对象数据。 我们也可以嵌套JSON对象，它还提供了一种表示数组的简便方法。

Java JSON (Java JSON)

JSON is widely used in web applications or as server response because it’s lightweight and more compact than XML. JSON objects are easy to read and write and most of the technologies provide support for JSON objects. That’s why JSON in Java web services are very popular.

JSON被广泛用于Web应用程序或服务器响应，因为它比XML轻巧且紧凑。 JSON对象易于读写，并且大多数技术都提供对JSON对象的支持。 这就是Java Web服务中JSON非常流行的原因。

JSR353 finally made into Java EE 7 and it’s the Java JSON processing API. jsonp is the reference implementation for Java JSON Processing API. We can use this in maven project by adding following dependency.

JSR353最终被制成Java EE 7，它是Java JSON处理API。 jsonp是Java JSON处理API的参考实现。 我们可以在maven项目中通过添加以下依赖项来使用它。

<dependency><groupId>org.glassfish</groupId><artifactId>javax.json</artifactId><version>1.0.2</version>
</dependency>

If you are using GlassFish 4.0 then you can keep the scope as provided because it’s already included in the server.

如果您使用的是GlassFish 4.0，则可以保留提供的范围，因为它已包含在服务器中。

JSON API provides two ways for JSON processing:

JSON API提供了两种JSON处理方式：

1. Object Model API – It’s similar to DOM Parser and good for small objects.对象模型API –与DOM分析器相似，适用于小型对象。
2. Streaming API – It’s similar to StaX Parser and good for large objects where you don’t want to keep whole object in memory.流API –与StaX Parser相似， 适用于不想将整个对象保留在内存中的大型对象。

Some important interfaces of Java JSON API are:

Java JSON API的一些重要接口是：

1. javax.json.JsonReader: We can use this to read JSON object or an array to JsonObject. We can get JsonReader from Json class or JsonReaderFactory.javax.json.JsonReader ：我们可以使用它来读取JSON对象或JsonObject的数组。 我们可以从Json类或JsonReaderFactory获取JsonReader。
2. javax.json.JsonWriter: We can use this to write JSON object to output stream.javax.json.JsonWriter ：我们可以使用它编写JSON对象以输出流。
3. javax.json.stream.JsonParser: This works as a pull parser and provide streaming support for reading JSON objects.javax.json.stream.JsonParser ：这用作拉解析器，并提供流支持以读取JSON对象。
4. javax.json.stream.JsonGenerator: We can use this to write JSON object to output source in streaming way.javax.json.stream.JsonGenerator ：我们可以使用它来以流方式将JSON对象写入输出源。
5. javax.json.Json: This is the factory class for creating JSON processing objects. This class provides the most commonly used methods for creating these objects and their corresponding factories. The factory classes provide all the various ways to create these objects.javax.json.Json ：这是用于创建JSON处理对象的工厂类。 此类提供了创建这些对象及其相应工厂的最常用方法。 工厂类提供了创建这些对象的所有各种方式。
6. javax.json.JsonObject: JsonObject represents an immutable JSON object value.javax.json.JsonObject ：JsonObject表示一个不变的JSON对象值。

Let’s look into the usage of Java JSON API with simple program, we have a JSON object stored in a file employee.txt as;

让我们通过简单的程序来研究Java JSON API的用法，我们在一个名为employee.txt的文件中存储了一个JSON对象；

{"id":123,"name":"Pankaj Kumar","permanent":true,"address":{"street":"El Camino Real","city":"San Jose","zipcode":95014},"phoneNumbers":[9988664422, 1234567890],"role":"Developer"
}

We have java bean classes that represent above JSON format as:

我们有将上述JSON格式表示为的Java bean类：

package com.journaldev.model;import java.util.Arrays;public class Employee {private int id;private String name;private boolean permanent;private Address address;private long[] phoneNumbers;private String role;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public boolean isPermanent() {return permanent;}public void setPermanent(boolean permanent) {this.permanent = permanent;}public Address getAddress() {return address;}public void setAddress(Address address) {this.address = address;}public long[] getPhoneNumbers() {return phoneNumbers;}public void setPhoneNumbers(long[] phoneNumbers) {this.phoneNumbers = phoneNumbers;}public String getRole() {return role;}public void setRole(String role) {this.role = role;}@Overridepublic String toString(){StringBuilder sb = new StringBuilder();sb.append("***** Employee Details *****\n");sb.append("ID="+getId()+"\n");sb.append("Name="+getName()+"\n");sb.append("Permanent="+isPermanent()+"\n");sb.append("Role="+getRole()+"\n");sb.append("Phone Numbers="+Arrays.toString(getPhoneNumbers())+"\n");sb.append("Address="+getAddress());sb.append("\n*****************************");return sb.toString();}
}

package com.journaldev.model;public class Address {private String street;private String city;private int zipcode;public String getStreet() {return street;}public void setStreet(String street) {this.street = street;}public String getCity() {return city;}public void setCity(String city) {this.city = city;}public int getZipcode() {return zipcode;}public void setZipcode(int zipcode) {this.zipcode = zipcode;}@Overridepublic String toString(){return getStreet() + ", "+getCity()+", "+getZipcode();}
}

I have overridden the toString() method to return human readable String representation that we will use in our JSON implementation classes.

我重写了toString（）方法，以返回人类可读的String表示形式，该表示形式将在JSON实现类中使用。

Java JSON阅读示例 (Java JSON Read Example)

package com.journaldev.json;import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;import javax.json.Json;
import javax.json.JsonArray;
import javax.json.JsonObject;
import javax.json.JsonReader;
import javax.json.JsonValue;import com.journaldev.model.Address;
import com.journaldev.model.Employee;public class EmployeeJSONReader {public static final String JSON_FILE="employee.txt";public static void main(String[] args) throws IOException {InputStream fis = new FileInputStream(JSON_FILE);//create JsonReader objectJsonReader jsonReader = Json.createReader(fis);/*** We can create JsonReader from Factory alsoJsonReaderFactory factory = Json.createReaderFactory(null);jsonReader = factory.createReader(fis);*///get JsonObject from JsonReaderJsonObject jsonObject = jsonReader.readObject();//we can close IO resource and JsonReader nowjsonReader.close();fis.close();//Retrieve data from JsonObject and create Employee beanEmployee emp = new Employee();emp.setId(jsonObject.getInt("id"));emp.setName(jsonObject.getString("name"));emp.setPermanent(jsonObject.getBoolean("permanent"));emp.setRole(jsonObject.getString("role"));//reading arrays from jsonJsonArray jsonArray = jsonObject.getJsonArray("phoneNumbers");long[] numbers = new long[jsonArray.size()];int index = 0;for(JsonValue value : jsonArray){numbers[index++] = Long.parseLong(value.toString());}emp.setPhoneNumbers(numbers);//reading inner object from json objectJsonObject innerJsonObject = jsonObject.getJsonObject("address");Address address = new Address();address.setStreet(innerJsonObject.getString("street"));address.setCity(innerJsonObject.getString("city"));address.setZipcode(innerJsonObject.getInt("zipcode"));emp.setAddress(address);//print employee bean informationSystem.out.println(emp);}}

The implementation is straight forward and feels similar as getting parameters from HashMap. JsonReaderFactory implements Factory Design Pattern. Once we execute above program, we get following output.

该实现很简单，感觉就像从HashMap获取参数一样。 JsonReaderFactory实现了工厂设计模式 。 一旦执行了上面的程序，我们将得到以下输出。

***** Employee Details *****
ID=123
Name=Pankaj Kumar
Permanent=true
Role=Developer
Phone Numbers=[9988664422, 1234567890]
Address=El Camino Real, San Jose, 95014
*****************************

Java JSON编写示例 (Java JSON Write Example)

package com.journaldev.json;import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.OutputStream;import javax.json.Json;
import javax.json.JsonArrayBuilder;
import javax.json.JsonObject;
import javax.json.JsonObjectBuilder;
import javax.json.JsonWriter;import com.journaldev.model.Address;
import com.journaldev.model.Employee;public class EmployeeJSONWriter {public static void main(String[] args) throws FileNotFoundException {Employee emp = createEmployee();JsonObjectBuilder empBuilder = Json.createObjectBuilder();JsonObjectBuilder addressBuilder = Json.createObjectBuilder();JsonArrayBuilder phoneNumBuilder = Json.createArrayBuilder();for (long phone : emp.getPhoneNumbers()) {phoneNumBuilder.add(phone);}addressBuilder.add("street", emp.getAddress().getStreet()).add("city", emp.getAddress().getCity()).add("zipcode", emp.getAddress().getZipcode());empBuilder.add("id", emp.getId()).add("name", emp.getName()).add("permanent", emp.isPermanent()).add("role", emp.getRole());empBuilder.add("phoneNumbers", phoneNumBuilder);empBuilder.add("address", addressBuilder);JsonObject empJsonObject = empBuilder.build();System.out.println("Employee JSON String\n"+empJsonObject);//write to fileOutputStream os = new FileOutputStream("emp.txt");JsonWriter jsonWriter = Json.createWriter(os);/*** We can get JsonWriter from JsonWriterFactory alsoJsonWriterFactory factory = Json.createWriterFactory(null);jsonWriter = factory.createWriter(os);*/jsonWriter.writeObject(empJsonObject);jsonWriter.close();}public static Employee createEmployee() {Employee emp = new Employee();emp.setId(100);emp.setName("David");emp.setPermanent(false);emp.setPhoneNumbers(new long[] { 123456, 987654 });emp.setRole("Manager");Address add = new Address();add.setCity("Bangalore");add.setStreet("BTM 1st Stage");add.setZipcode(560100);emp.setAddress(add);return emp;}}

Once we run above application, we get following response:

一旦我们在应用程序上运行，我们将得到以下响应：

Employee JSON String
{"id":100,"name":"David","permanent":false,"role":"Manager","phoneNumbers":[123456,987654],"address":{"street":"BTM 1st Stage","city":"Bangalore","zipcode":560100}}

JSON object is also getting saved in emp.txt file. JsonObjectBuilder implements builder pattern that makes it very easy to use.

JSON对象也被保存在emp.txt文件中。 JsonObjectBuilder实现了易于使用的构建器模式 。

Java JSON解析器示例 (Java JSON Parser Example)

Java JsonParser is a pull parser and we read the next element with next() method that returns an Event object. javax.json.stream.JsonParser.Event is an Enum that makes it type-safe and easy to use. We can use in switch case to set our java bean properties.

Java JsonParser是拉式解析器，我们使用next（）方法读取下一个元素，该方法返回一个Event对象。 javax.json.stream.JsonParser.Event是一个枚举 ，使其类型安全且易于使用。 我们可以在switch情况下使用来设置我们的java bean属性。

package com.journaldev.json;import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;import javax.json.Json;
import javax.json.stream.JsonParser;
import javax.json.stream.JsonParser.Event;import com.journaldev.model.Address;
import com.journaldev.model.Employee;public class EmployeeJSONParser {public static final String FILE_NAME = "employee.txt";public static void main(String[] args) throws IOException {InputStream fis = new FileInputStream(FILE_NAME);JsonParser jsonParser = Json.createParser(fis);/*** We can create JsonParser from JsonParserFactory also with below code* JsonParserFactory factory = Json.createParserFactory(null);* jsonParser = factory.createParser(fis);*/Employee emp = new Employee();Address address = new Address();String keyName = null;List<Long> phoneNums = new ArrayList<Long>();while (jsonParser.hasNext()) {Event event = jsonParser.next();switch (event) {case KEY_NAME:keyName = jsonParser.getString();break;case VALUE_STRING:setStringValues(emp, address, keyName, jsonParser.getString());break;case VALUE_NUMBER:setNumberValues(emp, address, keyName, jsonParser.getLong(), phoneNums);break;case VALUE_FALSE:setBooleanValues(emp, address, keyName, false);break;case VALUE_TRUE:setBooleanValues(emp, address, keyName, true);break;case VALUE_NULL:// don't set anythingbreak;default:// we are not looking for other events}}emp.setAddress(address);long[] nums = new long[phoneNums.size()];int index = 0;for(Long l :phoneNums){nums[index++] = l;}emp.setPhoneNumbers(nums);System.out.println(emp);//close resourcesfis.close();jsonParser.close();}private static void setNumberValues(Employee emp, Address address,String keyName, long value, List<Long> phoneNums) {switch(keyName){case "zipcode":address.setZipcode((int)value);break;case "id":emp.setId((int) value);break;case "phoneNumbers":phoneNums.add(value);break;default:System.out.println("Unknown element with key="+keyName);  }}private static void setBooleanValues(Employee emp, Address address,String key, boolean value) {if("permanent".equals(key)){emp.setPermanent(value);}else{System.out.println("Unknown element with key="+key);}}private static void setStringValues(Employee emp, Address address,String key, String value) {switch(key){case "name":emp.setName(value);break;case "role":emp.setRole(value);break;case "city":address.setCity(value);break;case "street":address.setStreet(value);break;default:System.out.println("Unknown Key="+key);}}}

The major complexity comes when we need to write the logic to parse the data and sometimes it can get complex.

当我们需要编写逻辑来解析数据时，有时会变得很复杂，这是主要的复杂性。

Since we are reading the same file as JsonReader, the output is same as EmployeeJsonReader program.

由于我们正在读取与JsonReader相同的文件，因此输出与EmployeeJsonReader程序相同。

Java JsonGenerator示例 (Java JsonGenerator Example)

package com.journaldev.json;import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;import javax.json.Json;
import javax.json.stream.JsonGenerator;import com.journaldev.model.Employee;public class EmployeeJSONGenerator {public static void main(String[] args) throws IOException {OutputStream fos = new FileOutputStream("emp_stream.txt");JsonGenerator jsonGenerator = Json.createGenerator(fos);/*** We can get JsonGenerator from Factory class also* JsonGeneratorFactory factory = Json.createGeneratorFactory(null);* jsonGenerator = factory.createGenerator(fos);*/Employee emp = EmployeeJSONWriter.createEmployee();jsonGenerator.writeStartObject(); // {jsonGenerator.write("id", emp.getId()); // "id":123jsonGenerator.write("name", emp.getName());jsonGenerator.write("role", emp.getRole());jsonGenerator.write("permanent", emp.isPermanent());jsonGenerator.writeStartObject("address") //start of address object.write("street", emp.getAddress().getStreet()).write("city",emp.getAddress().getCity()).write("zipcode",emp.getAddress().getZipcode()).writeEnd(); //end of address objectjsonGenerator.writeStartArray("phoneNumbers"); //start of phone num arrayfor(long num : emp.getPhoneNumbers()){jsonGenerator.write(num);}jsonGenerator.writeEnd(); // end of phone num arrayjsonGenerator.writeEnd(); // }jsonGenerator.close();}}

JsonGenerator is very easy to use and provides good performance for large data.

JsonGenerator非常易于使用，并为大数据提供良好的性能。

That’s all for Java JSON Processing API. We learned about Java JSON Parser, Read and Write examples. You can download java project from below link and play around with it.

Java JSON处理API就是这样。 我们了解了Java JSON解析器，读取和写入示例。 您可以从下面的链接下载Java项目并进行试用。

References:

参考文献：

JSONLint – Great web tool to validate JSON data
JSON Processing Reference Implementation
JSR353 JCP Page

JSONLint –验证JSON数据的出色网络工具
JSON处理参考实现
JSR353 JCP页面

翻译自: https://www.journaldev.com/2315/java-json-example

java封装json串示例