Google Gson测试对象序列化/反序列化
写在前面
一、简单测试
1.1、基本类型序列化与反序列化
@Test
public void t1() {
// Serialization
Gson gson = new Gson();
System.out.println(gson.toJson(1));
System.out.println(gson.toJson("abcd"));
System.out.println(gson.toJson(new Long(10)));
int[] values = {1};
System.out.println(gson.toJson(values));
// Deserialization
int o1 = gson.fromJson("1", int.class);
Integer o2 = gson.fromJson("1", Integer.class);
Long o3 = gson.fromJson("1", Long.class);
Boolean o4 = gson.fromJson("false", Boolean.class);
String o5 = gson.fromJson("\"abc\"", String.class);
String[] anotherStr = gson.fromJson("[\"abc\"]", String[].class);
}-
- 1
- “abcd”
- 10
- [1]
1.2、Object 示例
/** * Object Example * {"value1":1,"value2":"abc"} */
@Test
public void t2() {
// Serialization
BagOfPrimitives obj = new BagOfPrimitives();
Gson gson = new Gson();
String json = gson.toJson(obj);
System.out.println(json);
// Deserialization
BagOfPrimitives obj2 = gson.fromJson(json, BagOfPrimitives.class);
System.out.println(obj2.toString());
}需要注意： Gson可以很容易地序列化和反序列化静态嵌套类。
但是，不能自动反序列化纯内部类，因为它们的无参数构造函数还需要一个对包含对象的引用，
而在反序列化时这个引用是不可用的。可以通过使内部类为静态或为其提供自定义InstanceCreator来解决这个问题。这里有一个例子:
// public class InstanceCreatorForB implements InstanceCreator<NestedA.B> {
// private final A a;
// public InstanceCreatorForB(A a) {
// this.a = a;
// }
// public A.B createInstance(Type type) {
// return a.new B();
// }
// }1.3、数组 示例
@Test
public void t3() {
Gson gson = new Gson();
int[] ints = {1, 2, 3, 4, 5};
String[] strings = {"abc", "def", "ghi"};
// Serialization
gson.toJson(ints); // ==> [1,2,3,4,5]
gson.toJson(strings); // ==> ["abc", "def", "ghi"]
// Deserialization
int[] ints2 = gson.fromJson("[1,2,3,4,5]", int[].class);
}1.4、数组 示例
@Test
public void t4() {
Gson gson = new Gson();
Collection<Integer> ints = Lists.newArrayList(1, 2, 3, 4, 5);
// Serialization
String json = gson.toJson(ints); // ==> json is [1,2,3,4,5]
// Deserialization
Type collectionType = new TypeToken<Collection<Integer>>() {
}.getType();
Collection<Integer> ints2 = gson.fromJson(json, collectionType);
}1.5、泛型的序列化和反序列化
class Foo<T> {
T value;
}
class Bar {
String value;
}
@Test
public void t5() {
Gson gson = new Gson();
Foo<Bar> foo = new Foo<Bar>();
// 错误示例
String s = gson.toJson(foo);// 不是很正确
gson.fromJson(s, foo.getClass()); // 失败
// 以下是正确序列化/反序列化
Type fooType = new TypeToken<Foo<Bar>>() {
}.getType();
String s1 = gson.toJson(foo, fooType);
gson.fromJson(s1, fooType);
}1.6、混合类型 集合，如 [‘hello’,5,{name:‘GREETINGS’,source:‘guest’}]
1.7、格式化
/** * pretty style * <p> * { * "name": "GREETINGS", * "source": "guest" * } * { * "name": "GREETINGS" * } */
@Test
public void t7() {
Event event = new Event("GREETINGS", "guest");
Event event2 = new Event("GREETINGS", null);
Gson gson = new GsonBuilder().setPrettyPrinting().create();
String jsonOutput = gson.toJson(event);
String jsonOutput2 = gson.toJson(event2);
System.out.println(jsonOutput);
System.out.println(jsonOutput2);
}
/** * 空值 赋 null * {"name":"GREETINGS","source":null} */
@Test
public void t8() {
Event event2 = new Event("GREETINGS", null);
Gson gson = new GsonBuilder().serializeNulls().create();
String jsonOutput2 = gson.toJson(event2);
System.out.println(jsonOutput2);
}
/** * 版本控制 * {"newField":"new","field":"old"} * <p> * {"newerField":"newer","newField":"new","field":"old"} */
@Test
public void t9() {
Gson gson = new GsonBuilder().setVersion(1.0).create();
VersionedClass versionedObject = new VersionedClass();
String jsonOutput = gson.toJson(versionedObject);
System.out.println(jsonOutput);
System.out.println();
gson = new Gson();
jsonOutput = gson.toJson(versionedObject);
System.out.println(jsonOutput);
}
/** * 自定义命名 * {"custom_naming":"first","SomeOtherField":"second"} */
@Test
public void t10() {
SomeObject someObject = new SomeObject("first", "second");
Gson gson = new GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE).create();
String jsonRepresentation = gson.toJson(someObject);
System.out.println(jsonRepresentation);
}
/** * 时间序列化 */
@Test
public void t11() {
Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ").create();
String date = "\"2013-02-10T13:45:30+0100\"";
Date test = gson.fromJson(date, Date.class);
System.out.println("date:" + test);
}二、Gson自定义序列化的实现
2.1、先介绍一下，Gson本身实现的常见的几种序列化实现
是的，Gson 本身只提供了这六种 ，关于驼峰式命名的转换，太有限了，先简单测试一下
- POJO
@Data
@AllArgsConstructor
public class UserNaming {
String Name;
String email_of_developer;
boolean isDeveloper;
int _ageOfDeveloper;
}- IDENTITY
/** * 原序列 * FieldNamingPolicy.IDENTITY 测试 * {"Name":"Norman","email_of_developer":"[email protected]","isDeveloper":true,"_ageOfDeveloper":26} */
@Test
public void t13() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.IDENTITY);
Gson gson = gsonBuilder.create();
UserNaming user = new UserNaming("Norman", "[email protected]", true, 26);
String usersJson = gson.toJson(user);
System.out.println(usersJson);
}- LOWER_CASE_WITH_UNDERSCORES
/** * 下划线 * FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES，测试 * {"name":"Norman","email_of_developer":"[email protected]","is_developer":true,"_age_of_developer":26} */
@Test
public void t14() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
Gson gson = gsonBuilder.create();
UserNaming user = new UserNaming("Norman", "[email protected]", true, 26);
String usersJson = gson.toJson(user);
System.out.println(usersJson);
}- LOWER_CASE_WITH_DASHES
/** * 驼峰中横线 * FieldNamingPolicy.LOWER_CASE_WITH_DASHES，测试 * {"name":"Norman","email_of_developer":"[email protected]","is-developer":true,"_age-of-developer":26} */
@Test
public void t15() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_DASHES);
Gson gson = gsonBuilder.create();
UserNaming user = new UserNaming("Norman", "[email protected]", true, 26);
String usersJson = gson.toJson(user);
System.out.println(usersJson);
}- UPPER_CAMEL_CASE
/** * 驼峰首字母大写 * FieldNamingPolicy.UPPER_CAMEL_CASE，测试 * {"Name":"Norman","Email_of_developer":"[email protected]","IsDeveloper":true,"_AgeOfDeveloper":26} */
@Test
public void t16() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE);
Gson gson = gsonBuilder.create();
UserNaming user = new UserNaming("Norman", "[email protected]", true, 26);
String usersJson = gson.toJson(user);
System.out.println(usersJson);
}2.2、自定义 字段转换策略
- UPPER_CAMEL_CASE
/** * 驼峰转空格 * FieldNamingPolicy.UPPER_CAMEL_CASE，测试 * {"Name":"Norman","Email_of_developer":"[email protected]","Is Developer":true,"_Age Of Developer":26} */
@Test
public void t17() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE_WITH_SPACES);
Gson gson = gsonBuilder.create();
UserNaming user = new UserNaming("Norman", "[email protected]", true, 26);
String usersJson = gson.toJson(user);
System.out.println(usersJson);
}- 自定义 FieldNamingStrategy
/** * 自定义 - “”替换下划线 */
@Test
public void t18() {
FieldNamingStrategy customPolicy = new FieldNamingStrategy() {
@Override
public String translateName(Field f) {
return f.getName().replace("_", "");
}
};
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingStrategy(customPolicy);
Gson gson = gsonBuilder.create();
UserNaming user = new UserNaming("Norman", "[email protected]", true, 26);
String usersJson = gson.toJson(user);
System.out.println(usersJson);
}- 自定义2 FieldNamingStrategy
/** * 自定义字段 转换 * {"Name":"Norman","emailOfDeveloper":"[email protected]","isDeveloper":true,"Ageofdeveloper":26} */
@Test
public void t19() {
FieldNamingStrategy customPolicy = new FieldNamingStrategy() {
@Override
public String translateName(Field f) {
return StrUtil.toCamelCase(f.getName());
}
};
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setFieldNamingStrategy(customPolicy);
Gson gson = gsonBuilder.create();
UserNaming user = new UserNaming("Norman", "[email protected]", true, 26);
String usersJson = gson.toJson(user);
System.out.println(usersJson);
}