GSON - 序列化和反序列化枚举

转x33g5p2x  于2022-10-07 转载在 其他  
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在这篇文章中，我们将向您展示如何将枚举类型序列化和反序列化为JSON表示。

GSON的Maven依赖性

要在Maven2/3中使用Gson，你可以通过添加以下依赖项来使用Maven Central中的Gson版本。

  1. <dependencies>
  2.     <!--  Gson: Java to Json conversion -->
  3.     <dependency>
  4.       <groupId>com.google.code.gson</groupId>
  5.       <artifactId>gson</artifactId>
  6.       <version>2.8.5</version>
  7.       <scope>compile</scope>
  8.     </dependency>
  9. </dependencies>

让我们先创建Project POJO类和ProjectStatus枚举，我们将在接下来的例子中使用这个类。

  1. enum ProjectStatus {
  2.  NEW, OPEN, PROGRESS, HOLD, COMPLETED, CLOSED
  3. }
  5. class Project {
  6.     private int projectId;
  7.     private String projectName;
  8.     private String projectDesc;
  9.     private ProjectStatus projectStatus;
  11.     public Project(int projectId, String projectName, String projectDesc, ProjectStatus projectStatus) {
  12.         super();
  13.         this.projectId = projectId;
  14.         this.projectName = projectName;
  15.         this.projectDesc = projectDesc;
  16.         this.projectStatus = projectStatus;
  17.     }
  19.     public int getProjectId() {
  20.         return projectId;
  21.     }
  23.     public void setProjectId(int projectId) {
  24.         this.projectId = projectId;
  25.     }
  27.     public String getProjectName() {
  28.         return projectName;
  29.     }
  31.     public void setProjectName(String projectName) {
  32.         this.projectName = projectName;
  33.     }
  35.     public String getProjectDesc() {
  36.         return projectDesc;
  37.     }
  39.     public void setProjectDesc(String projectDesc) {
  40.         this.projectDesc = projectDesc;
  41.     }
  43.     public ProjectStatus getProjectStatus() {
  44.         return projectStatus;
  45.     }
  47.     public void setProjectStatus(ProjectStatus projectStatus) {
  48.         this.projectStatus = projectStatus;
  49.     }
  51.     @Override
  52.     public String toString() {
  53.         return "Project [projectId=" + projectId + ", projectName=" + projectName + ", projectDesc=" + projectDesc +
  54.             ", projectStatus=" + projectStatus + "]";
  55.     }
  56. }

串行化枚举类型

  1. public class GSONEnumExamples {
  2.     public static void main(String[] args) {
  3.         serializeEnumGson();
  4.     }
  6.     public static void serializeEnumGson() {
  7.         Project project = new Project(100, "CMS", "Content Management System", ProjectStatus.NEW);
  8.         Gson gson = new GsonBuilder().setPrettyPrinting().create();
  9.         String result = gson.toJson(project);
  10.         System.out.println(result);
  11.     }
  12. }

输出。

  1. {
  2.   "projectId": 100,
  3.   "projectName": "CMS",
  4.   "projectDesc": "Content Management System",
  5.   "projectStatus": "NEW"
  6. }

反序列化枚举类型

  1. public class GSONEnumExamples {
  2.     public static void main(String[] args) {
  3.         deserializeEnumGson();
  4.     }
  6.     public static void deserializeEnumGson() {
  7.         String input = "{\r\n" +
  8.             "  \"projectId\": 100,\r\n" +
  9.             "  \"projectName\": \"CMS\",\r\n" +
  10.             "  \"projectDesc\": \"Content Management System\",\r\n" +
  11.             "  \"projectStatus\": \"NEW\"\r\n" +
  12.             "}";
  13.         Gson gson = new GsonBuilder().create();
  14.         Project project = gson.fromJson(input, Project.class);
  15.         System.out.println(project.toString());
  16.     }
  17. }

输出。

  1. Project [projectId=100, projectName=CMS, projectDesc=Content Management System, projectStatus=NEW]

完整的例子供参考

  1. package net.javaguides.gson;
  3. import com.google.gson.Gson;
  4. import com.google.gson.GsonBuilder;
  6. public class GSONEnumExamples {
  7.     public static void main(String[] args) {
  8.         serializeEnumGson();
  9.         deserializeEnumGson();
  10.     }
  12.     public static void serializeEnumGson() {
  13.         Project project = new Project(100, "CMS", "Content Management System", ProjectStatus.NEW);
  14.         Gson gson = new GsonBuilder().setPrettyPrinting().create();
  15.         String result = gson.toJson(project);
  16.         System.out.println(result);
  17.     }
  19.     public static void deserializeEnumGson() {
  20.         String input = "{\r\n" +
  21.             "  \"projectId\": 100,\r\n" +
  22.             "  \"projectName\": \"CMS\",\r\n" +
  23.             "  \"projectDesc\": \"Content Management System\",\r\n" +
  24.             "  \"projectStatus\": \"NEW\"\r\n" +
  25.             "}";
  26.         Gson gson = new GsonBuilder().create();
  27.         Project project = gson.fromJson(input, Project.class);
  28.         System.out.println(project.toString());
  29.     }
  30. }
  32. enum ProjectStatus {
  33.     NEW,
  34.     OPEN,
  35.     PROGRESS,
  36.     HOLD,
  37.     COMPLETED,
  38.     CLOSED
  39. }
  41. class Project {
  42.     private int projectId;
  43.     private String projectName;
  44.     private String projectDesc;
  45.     private ProjectStatus projectStatus;
  47.     public Project(int projectId, String projectName, String projectDesc, ProjectStatus projectStatus) {
  48.         super();
  49.         this.projectId = projectId;
  50.         this.projectName = projectName;
  51.         this.projectDesc = projectDesc;
  52.         this.projectStatus = projectStatus;
  53.     }
  55.     public int getProjectId() {
  56.         return projectId;
  57.     }
  59.     public void setProjectId(int projectId) {
  60.         this.projectId = projectId;
  61.     }
  63.     public String getProjectName() {
  64.         return projectName;
  65.     }
  67.     public void setProjectName(String projectName) {
  68.         this.projectName = projectName;
  69.     }
  71.     public String getProjectDesc() {
  72.         return projectDesc;
  73.     }
  75.     public void setProjectDesc(String projectDesc) {
  76.         this.projectDesc = projectDesc;
  77.     }
  79.     public ProjectStatus getProjectStatus() {
  80.         return projectStatus;
  81.     }
  83.     public void setProjectStatus(ProjectStatus projectStatus) {
  84.         this.projectStatus = projectStatus;
  85.     }
  87.     @Override
  88.     public String toString() {
  89.         return "Project [projectId=" + projectId + ", projectName=" + projectName + ", projectDesc=" + projectDesc +
  90.             ", projectStatus=" + projectStatus + "]";
  91.     }
  92. }

输出。

  1. {
  2.   "projectId": 100,
  3.   "projectName": "CMS",
  4.   "projectDesc": "Content Management System",
  5.   "projectStatus": "NEW"
  6. }
  7. Project [projectId=100, projectName=CMS, projectDesc=Content Management System, projectStatus=NEW]

使用@SerializedName注解对枚举进行序列化和反序列化

默认情况下，Gson用**小写的名字来序列化枚举。如果这还不够，你想要一些其他的字符串或整数值，那么可以看看@SerializedName注解。Gson可以使用@SerializedName注解对枚举进行序列化和反序列化。如果我们用@SerializedName注解一个枚举，我们可以提供一个值，当GSON将JSON序列化或反序列化为Java对象时，这个值将被映射。

让我们从一个例子开始。在下面的类中，我们用@SerializedName注释了状态枚举。我们可以用一个值来映射这些枚举，这个值在序列化时被使用。当反序列化时，如果指定了这个值，它将使用正确的枚举。如果没有找到这个值，它将返回 "null"。
让我们给ProjectStatus枚举添加一个@SerializedName注解，如下所示。

  1. enum ProjectStatus {
  2.     @SerializedName("1")
  3.     NEW, @SerializedName("2")
  4.     OPEN, @SerializedName("3")
  5.     PROGRESS, @SerializedName("4")
  6.     HOLD, @SerializedName("5")
  7.     COMPLETED, @SerializedName("6")
  8.     CLOSED
  9. }

让我们写一个完整的例子，使用@SerializedName注解对枚举进行序列化和反序列化。

  1. package net.javaguides.gson;
  3. import com.google.gson.Gson;
  4. import com.google.gson.GsonBuilder;
  5. import com.google.gson.annotations.SerializedName;
  7. public class GSONEnumExamples {
  8.     public static void main(String[] args) {
  9.         serializeEnumGson();
  10.         deserializeEnumGson();
  11.     }
  13.     public static void serializeEnumGson() {
  14.         Project project = new Project(100, "CMS", "Content Management System", ProjectStatus.NEW);
  15.         Gson gson = new GsonBuilder().setPrettyPrinting().create();
  16.         String result = gson.toJson(project);
  17.         System.out.println(result);
  18.     }
  20.     public static void deserializeEnumGson() {
  21.         String input = "{\r\n" + "  \"projectId\": 100,\r\n" + "  \"projectName\": \"CMS\",\r\n" +
  22.             "  \"projectDesc\": \"Content Management System\",\r\n" + "  \"projectStatus\": \"1\"\r\n" + "}";
  23.         Gson gson = new GsonBuilder().create();
  24.         Project project = gson.fromJson(input, Project.class);
  25.         System.out.println(project.toString());
  26.     }
  27. }
  29. enum ProjectStatus {
  30.     @SerializedName("1")
  31.     NEW, @SerializedName("2")
  32.     OPEN, @SerializedName("3")
  33.     PROGRESS, @SerializedName("4")
  34.     HOLD, @SerializedName("5")
  35.     COMPLETED, @SerializedName("6")
  36.     CLOSED
  37. }
  39. class Project {
  40.     private int projectId;
  41.     private String projectName;
  42.     private String projectDesc;
  43.     private ProjectStatus projectStatus;
  45.     public Project(int projectId, String projectName, String projectDesc, ProjectStatus projectStatus) {
  46.         super();
  47.         this.projectId = projectId;
  48.         this.projectName = projectName;
  49.         this.projectDesc = projectDesc;
  50.         this.projectStatus = projectStatus;
  51.     }
  53.     public int getProjectId() {
  54.         return projectId;
  55.     }
  57.     public void setProjectId(int projectId) {
  58.         this.projectId = projectId;
  59.     }
  61.     public String getProjectName() {
  62.         return projectName;
  63.     }
  65.     public void setProjectName(String projectName) {
  66.         this.projectName = projectName;
  67.     }
  69.     public String getProjectDesc() {
  70.         return projectDesc;
  71.     }
  73.     public void setProjectDesc(String projectDesc) {
  74.         this.projectDesc = projectDesc;
  75.     }
  77.     public ProjectStatus getProjectStatus() {
  78.         return projectStatus;
  79.     }
  81.     public void setProjectStatus(ProjectStatus projectStatus) {
  82.         this.projectStatus = projectStatus;
  83.     }
  85.     @Override
  86.     public String toString() {
  87.         return "Project [projectId=" + projectId + ", projectName=" + projectName + ", projectDesc=" + projectDesc +
  88.             ", projectStatus=" + projectStatus + "]";
  89.     }
  90. }

输出：

  1. {
  2.   "projectId": 100,
  3.   "projectName": "CMS",
  4.   "projectDesc": "Content Management System",
  5.   "projectStatus": "1"
  6. }
  7. Project [projectId=100, projectName=CMS, projectDesc=Content Management System, projectStatus=NEW]

版权说明 : 本文为转载文章, 版权归原作者所有 版权申明

原文链接 : https://www.javaguides.net/2018/10/gson-serializing-and-deserializing-enums.html

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