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  • Google Gson 使用简介

    如何将数组转化为 json 串?

    下面的例子中我们示例如何将一个数据转换成 json 串,并使用 Gson.toJson() 方法将数组序列化为 JSON,以及Gson.fromJson() 方法将 JSON 串反序列化为 java 数组。

    复制代码
    import com.google.gson.Gson;
    
    public class ArrayToJson {
        public static void main(String[] args) {
            int[] numbers = {1, 1, 2, 3, 5, 8, 13};
            String[] days = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
    
            //
            // Create a new instance of Gson
            //
            Gson gson = new Gson();
    
            //
            // Convert numbers array into JSON string.
            //
            String numbersJson = gson.toJson(numbers);
    
            //
            // Convert strings array into JSON string
            //
            String daysJson = gson.toJson(days);
            System.out.println("numbersJson = " + numbersJson);
            System.out.println("daysJson = " + daysJson);
    
            //
            // Convert from JSON string to a primitive array of int.
            //
            int[] fibonacci = gson.fromJson(numbersJson, int[].class);
            for (int i = 0; i < fibonacci.length; i++) {
                System.out.print(fibonacci[i] + " ");
            }
            System.out.println("");
    
            //
            // Convert from JSON string to a string array.
            //
            String[] weekDays = gson.fromJson(daysJson, String[].class);
            for (int i = 0; i < weekDays.length; i++) {
                System.out.print(weekDays[i] + " ");
            }
            System.out.println("");
    
            //
            // Converting multidimensional array into JSON
            //
            int[][] data = {{1, 2, 3}, {3, 4, 5}, {4, 5, 6}};
            String json = gson.toJson(data);
            System.out.println("Data = " + json);
    
            //
            // Convert JSON string into multidimensional array of int.
            //
            int[][] dataMap = gson.fromJson(json, int[][].class);
            for (int i = 0; i < data.length; i++) {
                for (int j = 0; j < data[i].length; j++) {
                    System.out.print(data[i][j] + " ");
                }
                System.out.println("");
            }
        }
    }
    复制代码

    以下是输出结果:

    复制代码
    numbersJson = [1,1,2,3,5,8,13]
    daysJson = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat"]
    1 1 2 3 5 8 13 
    Sun Mon Tue Wed Thu Fri Sat 
    Data = [[1,2,3],[3,4,5],[4,5,6]]
    1 2 3 
    3 4 5
    复制代码

    如何将集合转化为 json 串?

    下面的例子中我们示例如何将Java集合转换为符合 json 规则的字符串。

    复制代码
    import java.util.Date;
    
    public class Student {
        private String name;
        private String address;
        private Date dateOfBirth;
    
        public Student() {
        }
    
        public Student(String name, String address, Date dateOfBirth) {
            this.name = name;
            this.address = address;
            this.dateOfBirth = dateOfBirth;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getAddress() {
            return address;
        }
    
        public void setAddress(String address) {
            this.address = address;
        }
    
        public Date getDateOfBirth() {
            return dateOfBirth;
        }
    
        public void setDateOfBirth(Date dateOfBirth) {
            this.dateOfBirth = dateOfBirth;
        }
    }
    复制代码
    复制代码
    import com.google.gson.Gson;
    import com.google.gson.reflect.TypeToken;
    
    import java.lang.reflect.Type;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    
    public class CollectionToJson {
        public static void main(String[] args) {
            //
            // Converts a collection of string object into JSON string.
            //
            List<String> names = new ArrayList<String>();
            names.add("Alice");
            names.add("Bob");
            names.add("Carol");
            names.add("Mallory");
    
            Gson gson = new Gson();
            String jsonNames = gson.toJson(names);
            System.out.println("jsonNames = " + jsonNames);
    
            //
            // Converts a collection Student object into JSON string
            //
            Student a = new Student("Alice", "Apple St", new Date(2000, 10, 1));
            Student b = new Student("Bob", "Banana St", null);
            Student c = new Student("Carol", "Grape St", new Date(2000, 5, 21));
            Student d = new Student("Mallory", "Mango St", null);
    
            List<Student> students = new ArrayList<Student>();
            students.add(a);
            students.add(b);
            students.add(c);
            students.add(d);
    
            gson = new Gson();
            String jsonStudents = gson.toJson(students);
            System.out.println("jsonStudents = " + jsonStudents);
    
            //
            // Converts JSON string into a collection of Student object.
            //
            Type type = new TypeToken<List<Student>>(){}.getType();
            List<Student> studentList = gson.fromJson(jsonStudents, type);
    
            for (Student student : studentList) {
                System.out.println("student.getName() = " + student.getName());
            }
        }
    }
    复制代码

    以下是输出结果:

    复制代码
    jsonNames = ["Alice","Bob","Carol","Mallory"]
    jsonStudents = [{"name":"Alice","address":"Apple St","dateOfBirth":"Nov 1, 3900 12:00:00 AM"},{"name":"Bob","address":"Banana St"},{"name":"Carol","address":"Grape St","dateOfBirth":"Jun 21, 3900 12:00:00 AM"},{"name":"Mallory","address":"Mango St"}]
    student.getName() = Alice
    student.getName() = Bob
    student.getName() = Carol
    student.getName() = Mallory
    复制代码

    如何将Map转化为 json 串?

    下面的例子中我们示例如何将java.util.Map转化成 json 串,然后再将 json 串转换为java.util.Map

    复制代码
    import com.google.gson.Gson;
    import com.google.gson.reflect.TypeToken;
    
    import java.lang.reflect.Type;
    import java.util.HashMap;
    import java.util.Map;
    
    public class MapToJson {
        public static void main(String[] args) {
            Map<String, String> colours = new HashMap<String, String>();
            colours.put("BLACK", "#000000");
            colours.put("RED", "#FF0000");
            colours.put("GREEN", "#008000");
            colours.put("BLUE", "#0000FF");
            colours.put("YELLOW", "#FFFF00");
            colours.put("WHITE", "#FFFFFF");
    
            //
            // Convert a Map into JSON string.
            //
            Gson gson = new Gson();
            String json = gson.toJson(colours);
            System.out.println("json = " + json);
    
            //
            // Convert JSON string back to Map.
            //
            Type type = new TypeToken<Map<String, String>>(){}.getType();
            Map<String, String> map = gson.fromJson(json, type);
            for (String key : map.keySet()) {
                System.out.println("map.get = " + map.get(key));
            }
        }
    }
    复制代码

    以下是输出结果:

    复制代码
    json = {"WHITE":"#FFFFFF","BLUE":"#0000FF","YELLOW":"#FFFF00","GREEN":"#008000","BLACK":"#000000","RED":"#FF0000"}
    map.get = #FFFFFF
    map.get = #0000FF
    map.get = #FFFF00
    map.get = #008000
    map.get = #000000
    map.get = #FF0000
    复制代码

    如何将对象转换为 json 串?

    下面的例子中我们示例如何将一个 Student 对象转换成 json 串,实际操作中我们也可以将任意的 Java 类转换为 json 串,并且实施起来也非常简单,你仅仅需要创建一个 Gson 实例,然后传递将被转化为 json 串的对象,并调用该实例的 toJson 方法即可。

    复制代码
    import com.google.gson.Gson;
    
    import java.util.Calendar;
    
    public class StudentToJson {
        public static void main(String[] args) {
            Calendar dob = Calendar.getInstance();
            dob.set(2000, 1, 1, 0, 0, 0);
            Student student = new Student("Duke", "Menlo Park", dob.getTime());
    
            Gson gson = new Gson();
            String json = gson.toJson(student);
            System.out.println("json = " + json);
        }
    }
    复制代码
    复制代码
    import java.util.Date;
    
    public class Student {
        private String name;
        private String address;
        private Date dateOfBirth;
    
        public Student() {
        }
    
        public Student(String name, String address, Date dateOfBirth) {
            this.name = name;
            this.address = address;
            this.dateOfBirth = dateOfBirth;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getAddress() {
            return address;
        }
    
        public void setAddress(String address) {
            this.address = address;
        }
    
        public Date getDateOfBirth() {
            return dateOfBirth;
        }
    
        public void setDateOfBirth(Date dateOfBirth) {
            this.dateOfBirth = dateOfBirth;
        }
    }
    复制代码

    以下是输出结果:

    json = {"name":"Duke","address":"Menlo Park","dateOfBirth":"Feb 1, 2000 12:00:00 AM"}

    如何将 json 串转换为对象?

    下面的例子中我们示例如何 json 串转化成 Java对象。

    复制代码
    import com.google.gson.Gson;
    
    public class JsonToStudent {
        public static void main(String[] args) {
            String json = "{"name":"Duke","address":"Menlo Park","dateOfBirth":"Feb 1, 2000 12:00:00 AM"}";
    
            Gson gson = new Gson();
            Student student = gson.fromJson(json, Student.class);
    
            System.out.println("student.getName()        = " + student.getName());
            System.out.println("student.getAddress()     = " + student.getAddress());
            System.out.println("student.getDateOfBirth() = " + student.getDateOfBirth());
        }
    }
    复制代码

    以下是输出结果:

    student.getName()        = Duke
    student.getAddress()     = Menlo Park
    student.getDateOfBirth() = Tue Feb 01 00:00:00 CST 2000

    如何处理对象的字段?

    下面的例子中我们示例如何利用Gson处理一个对象的某一字段。

    复制代码
    import com.google.gson.Gson;
    
    import java.util.Calendar;
    
    public class GsonFieldExample {
        public static void main(String[] args) {
            Calendar dob = Calendar.getInstance();
            dob.set(1980, 10, 11);
            People people = new People("John", "350 Banana St.", dob.getTime());
            people.setSecret("This is a secret!");
    
            Gson gson = new Gson();
            String json = gson.toJson(people);
            System.out.println("json = " + json);
        }
    }
    复制代码
    复制代码
    import java.util.Date;
    
    public class People {
        private String name;
        private String address;
        private Date dateOfBirth;
        private Integer age;
        private transient String secret;
    
        public People(String name, String address, Date dateOfBirth) {
            this.name = name;
            this.address = address;
            this.dateOfBirth = dateOfBirth;
        }
    
        public String getSecret() {
            return secret;
        }
    
        public void setSecret(String secret) {
            this.secret = secret;
        }
    }
    复制代码

     以下是输出结果:

    json = {"name":"John","address":"350 Banana St.","dateOfBirth":"Nov 11, 1980 8:47:04 AM"}
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  • 原文地址:https://www.cnblogs.com/ihanliu/p/4724312.html
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