Jackson序列化和反序列化Json数据

Web技术发展的今天，Json和XML已经成为了web数据的事实标准，然而这种格式化的数据手工解析又非常麻烦，软件工程界永远不缺少工具，每当有需求的时候就会出现各种类库，框架以及工具来解决这些基础的问题，Jackson就是这些工具中的一个，使用这个工具开发者完全可以从手工结束Json数据的重复劳动中解放出来。使用Jackson首先需要下载相应的类库，如下的Maven dependency列出了完整的POM dependency。<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>${jackson-2-version}</version>
</dependency>

<！-- Just the annotations; use this dependency if you want to attach annotations
to classes without connecting them to the code. -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>${jackson-2-version}</version>
</dependency>

<！-- databinding; ObjectMapper, JsonNode and related classes are here -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson-2-version}</version>
</dependency>

<！-- smile （binary JSON）. Other artifacts in this group do other formats. -->
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-smile</artifactId>
<version>${jackson-2-version}</version>
</dependency>
<！-- JAX-RS provider -->
<dependency>
<groupId>com.fasterxml.jackson.jaxrs</groupId>
<artifactId>jackson-jaxrs-json-provider</artifactId>
<version>${jackson-2-version}</version>
</dependency>
<！-- Support for JAX-B annotations as additional configuration -->
<dependency>
<groupId>com.fasterxml.jackson.module</groupId>
<artifactId>jackson-module-jaxb-annotations</artifactId>
<version>${jackson-2-version}</version>
</dependency>比如我们需要解析的Json数据如下：{
"id": 123,
"name": "Pankaj",
"permanent": true,
"address": {
"street": "Albany Dr",
"city": "San Jose",
"zipcode": 95129
},
"phoneNumbers": [
123456,
],
"role": "Manager",
"cities": [
"Los Angeles",
"New York"
],
"properties": {
"age": "29 years",
"salary": "1000 USD"
}
}对应的Model Class 如下：import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class Employee {

private int id;
private String name;
private boolean permanent;
private Address address;
private long[] phoneNumbers;
private String role;
private List<String> cities;
private Map<String, String> properties;

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;
}

@Override
public String toString（）{
StringBuilder sb = new StringBuilder（）;
sb.append（"***** Employee Details ***** "）;
sb.append（"ID="+getId（）+" "）;
sb.append（"Name="+getName（）+" "）;
sb.append（"Permanent="+isPermanent（）+" "）;
sb.append（"Role="+getRole（）+" "）;
sb.append（"Phone Numbers="+Arrays.toString（getPhoneNumbers（））+" "）;
sb.append（"Address="+getAddress（）+" "）;
sb.append（"Cities="+Arrays.toString（getCities（）.toArray（））+" "）;
sb.append（"Properties="+getProperties（）+" "）;
sb.append（"*****************************"）;

return sb.toString（）;
}
public List<String> getCities（） {
return cities;
}
public void setCities（List<String> cities） {
this.cities = cities;
}
public Map<String, String> getProperties（） {
return properties;
}
public void setProperties（Map<String, String> properties） {
this.properties = properties;
}
}当我们需要操作Json数据的时候，如下代码示范了如何将Json数据反序列化为对象以及如何将对象序列化为Json数据。import java.io.File;
import java.io.IOException;
import java.io.StringWriter;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.node.ObjectNode;public class JacksonObjectMapperExample {

public static void main（String[] args） throws IOException {

//read json file data to String
byte[] jsonData = Files.readAllBytes（Paths.get（"C:\employee.txt"））;

//create ObjectMapper instance
ObjectMapper objectMapper = new ObjectMapper（）;

//convert json string to object
Employee emp = objectMapper.readValue（jsonData, Employee.class）;

System.out.println（"Employee Object "+emp）;

//convert Object to json string
Employee emp1 = createEmployee（）;
//configure Object mapper for pretty print
objectMapper.configure（SerializationFeature.INDENT_OUTPUT, true）;

//writing to console, can write to any output stream such as file
StringWriter stringEmp = new StringWriter（）;
objectMapper.writeValue（stringEmp, emp1）;
System.out.println（"Employee JSON is "+stringEmp）;
}

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）;

List<String> cities = new ArrayList<String>（）;
cities.add（"Los Angeles"）;
cities.add（"New York"）;
emp.setCities（cities）;

Map<String, String> props = new HashMap<String, String>（）;
props.put（"salary", "1000 Rs"）;
props.put（"age", "28 years"）;
emp.setProperties（props）;

return emp;
}

}结果如下：Employee Object
***** Employee Details *****
ID=123
Name=Pankaj
Permanent=true
Role=Manager
Phone Numbers=[123456, 987654]
Address=Albany Dr, San Jose, 95129
Cities=[Los Angeles, New York]
Properties={age=29 years, salary=1000 USD}
*****************************
Employee JSON is
{
"id" : 100,
"name" : "David",
"permanent" : false,
"address" : {
"street" : "BTM 1st Stage",
"city" : "Bangalore",
"zipcode" : 560100
},
"phoneNumbers" : [ 123456, 987654 ],
"role" : "Manager",
"cities" : [ "Los Angeles", "New York" ],
"properties" : {
"salary" : "1000 Rs",
"age" : "28 years"
}
}总结本文以一个完整的示例总结了Java对象序列化为Json对象和反序列化的过程，希望可以抛砖引玉对大家有所帮助。本文永久更新链接地址：http://www.linuxidc.com/Linux/2015-12/125904.htm