1. Gson使用其內置適配器執行對象的序列化/反序列化。它還支持自定義適配器。我們將討論如何創建自定義適配器以及如何使用它。

2. 創建自定義適配器

2.1. 通過擴展TypeAdapter類并將其傳遞給目標對象的類型來創建自定義適配器。重寫讀取和寫入方法以分別執行自定義反序列化和序列化。

class StudentAdapter extends TypeAdapter<Student> {@Overridepublic Student read(JsonReader reader) throws IOException {...}@Overridepublic void write(JsonWriter writer, Student student) throws IOException {} }

3. 注冊自定義適配器

3.1. 使用GsonBuilder注冊自定義適配器和使用創造GSON實例GsonBuilder。

GsonBuilder builder = new GsonBuilder(); builder.registerTypeAdapter(Student.class, new StudentAdapter()); Gson gson = builder.create();

4. 使用適配器

4.1. Gson現在將使用自定義適配器將Json文本轉換為對象, 反之亦然。

String jsonString = "{\"id\":1, \"name\":\"張三\"}"; Student student = gson.fromJson(jsonString, Student.class); System.out.println(student); jsonString = gson.toJson(student); System.out.println(jsonString);

5. 例子

5.1. 新建一個名為GsonAdapter的Java項目, 同時添加相關jar包。

5.2. 新建Student.java

package com.fj.a;public class Student {private int id;private String name;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 String toString() {return "Student [id = " + id + ", name = " + name + "]";} }

5.3. 新建StudentAdapter.java

package com.fj.a;import java.io.IOException; import com.google.gson.TypeAdapter; import com.google.gson.stream.JsonReader; import com.google.gson.stream.JsonToken; import com.google.gson.stream.JsonWriter;class StudentAdapter extends TypeAdapter<Student> {@Overridepublic Student read(JsonReader reader) throws IOException {Student student = new Student();reader.beginObject();String fieldname = null;while (reader.hasNext()) {JsonToken token = reader.peek();if (token.equals(JsonToken.NAME)) {fieldname = reader.nextName();}if ("id".equals(fieldname)) {token = reader.peek();student.setId(reader.nextInt());}if ("name".equals(fieldname)) {token = reader.peek();student.setName(reader.nextString());}}reader.endObject();return student;}@Overridepublic void write(JsonWriter writer, Student student) throws IOException {writer.beginObject();writer.name("id");writer.value(student.getId());writer.name("name");writer.value(student.getName());writer.endObject();} }

5.4. 新建App.java

package com.fj.a;import com.google.gson.Gson; import com.google.gson.GsonBuilder;public class App {public static void main(String args[]) {GsonBuilder builder = new GsonBuilder();builder.registerTypeAdapter(Student.class, new StudentAdapter());builder.setPrettyPrinting();Gson gson = builder.create();String jsonString = "{\"id\":1, \"name\":\"張三\"}";Student student = gson.fromJson(jsonString, Student.class);System.out.println(student);jsonString = gson.toJson(student);System.out.println(jsonString);} }

5.5. 運行App.java

總結

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