使用Gson解析常见json字符串

日常开发中常遇到的json字符串主要有三种：

1）简单的json object  字符串

      String jsonObjectStr = "{\"name\":\"zhangsan\",\"age\":\"18\"}";

2）json array 字符串

      String jsonArrayStr = "[{\"name\":\"zhangsan\",\"age\":\"18\"},{\"name\":\"lisi\",\"age\":\"28\"}]";

3）稍微复杂点的json object 字符串

      String jsonSpecialStr = "{\"school\":\"NanJingDaXue\",\"city\":\"najing\",\"peoples\":[{\"name\":\"zhangsan\",\"age\":\"18\"},{\"name\":\"zhangsan\",\"age\":\"18\"}]}";

解析json的方法很多，这里总结下使用Gson解析以上三种json字符串的方法：

1、首先新建一个maven工程，pom文件中引入gson的依赖项：

    
	    com.google.code.gson
	    gson
	    2.2.2
    

2、根据前面提到的json字符串结构，可定义反序列化对象People类、Students：

    package com.zgy.json.info;

    public class People
    {
        //name
        private String name;
    
        //age
        private String age;

	/**
	 * @return the name
	 */
	public String getName()
	{
		return name;
	}

	/**
	 * @param name the name to set
	 */
	public void setName(String name)
	{
		this.name = name;
	}

	/* (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString()
	{
		StringBuilder builder = new StringBuilder();
		builder.append("People [name=");
		builder.append(name);
		builder.append(", age=");
		builder.append(age);
		builder.append("]");
		return builder.toString();
	}
    }

    package com.zgy.json.info;

    import java.util.Arrays;
    import com.google.gson.annotations.SerializedName;

public class Students
{
	private String school;
	
	@SerializedName("city")  //注解，当json字符串中的字段定义和所需的不同时，可用注解标注
	private String city;
	
	private People [] peoples;

	/**
	 * @return the school
	 */
	public String getSchool()
	{
		return school;
	}

	/**
	 * @param school the school to set
	 */
	public void setSchool(String school)
	{
		this.school = school;
	}

	/* (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString()
	{
		StringBuilder builder = new StringBuilder();
		builder.append("Students [school=");
		builder.append(school);
		builder.append(", city=");
		builder.append(city);
		builder.append(", peoples=");
		builder.append(Arrays.toString(peoples));
		builder.append("]");
		return builder.toString();
	}
}

3、简单的json object  字符串的解析

Code: 

    String jsonObjectStr = "{\"name\":\"zhangsan\",\"age\":\"18\"}";
    Gson gson = new Gson();
    People people = gson.fromJson(jsonObjectStr, People.class);
    System.out.println(people.toString());

解析结果：

People [name=zhangsan, age=18]

4、json array 字符串的解析

Code:    

    String jsonArrayStr = "[{\"name\":\"zhangsan\",\"age\":\"18\"},{\"name\":\"lisi\",\"age\":\"28\"}]";
    Gson gson = new Gson();

    People[] peoples = gson.fromJson(jsonArrayStr, People[].class);

    for (People x : peoples)
    {
        System.out.println(x.toString());
    }

解析结果：

People [name=zhangsan, age=18]
People [name=lisi, age=28]

5、第三种复杂json
 

Code:    

String jsonSpecialStr = "{\"school\":\"NanJingDaXue\",\"city\":\"nanjing\",\"peoples\":[{\"name\":\"zhangsan\",\"age\":\"18\"},

                              {\"name\":\"lisi\",\"age\":\"28\"}]}";
    Gson gson = new Gson();

    Students students = gson.fromJson(jsonSpecialStr, Students.class);
    System.out.println(students.toString());

解析结果：

Students [school=NanJingDaXue, city=nanjing, peoples=[People [name=zhangsan, age=18], People [name=lisi, age=28]]]