您拥有非常复杂的JSON有效负载，其中相同的属性可能具有一个JSON object或JSON array多个对象。Gson默认情况下不会处理这种情况，因此我们需要为此类one-or- many属性实现自定义反序列化器。下面我创建了POJO代表您的JSON有效负载的简单模型：

class TestResponse {

    @SerializedName("test-run")
    private TestRun testRun;

    // other properties, getters, setters, toString
}

class TestRun {

    @SerializedName("test-suite")
    private List<TestSuite> testSuite;

    // other properties, getters, setters, toString
}

class TestSuite {
    private String result;
    private double duration;

    @SerializedName("test-suite")
    private List<TestSuite> testSuites;

    @SerializedName("test-case")
    private List<TestCase> testCases;

    // other properties, getters, setters, toString
}

class TestCase {

    private String fullname;

    // other properties, getters, setters, toString
}

如您所见test-suite，它test-case是List-es属性。让我们为这些属性实现自定义反序列化器：

class OneOrManyJsonDeserializer<E> implements JsonDeserializer<List<E>> {

    private final Class<E> clazz;

    public OneOrManyJsonDeserializer(Class<E> clazz) {
        this.clazz = clazz;
    }

    @Override
    public List<E> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        if (json instanceof JsonArray) {
            final JsonArray array = (JsonArray) json;
            final int size = array.size();
            if (size == 0) {
                return Collections.emptyList();
            }
            final List<E> suites = new ArrayList<>(size);
            for (int i = 0; i < size; i++) {
                suites.add(context.deserialize(array.get(i), clazz));
            }

            return suites;
        }

        E suite = context.deserialize(json, clazz);
        return Collections.singletonList(suite);
    }
}

Class<E>在运行时需要正确地反序列化JSON object。之后，让我们创建和自定义Gson实例：

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonArray;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.annotations.SerializedName;
import com.google.gson.reflect.TypeToken;

import java.io.File;
import java.io.FileReader;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class GsonApp {

    public static void main(String[] args) throws Exception {
        File jsonFile = new File("./resource/test.json").getAbsoluteFile();

        Type testCaseListType = new TypeToken<List<TestCase>>() {}.getType();
        Type testSuiteListType = new TypeToken<List<TestSuite>>() {}.getType();
        Gson gson = new GsonBuilder()
                .registerTypeAdapter(testCaseListType, new OneOrManyJsonDeserializer<>(TestCase.class))
                .registerTypeAdapter(testSuiteListType, new OneOrManyJsonDeserializer<>(TestSuite.class))
                .setPrettyPrinting()
                .create();

        TestResponse response = gson.fromJson(new FileReader(jsonFile), TestResponse.class);
        System.out.println(response);
    }
}

如您所见，我们为每种one-to-many类型注册了两个实例。我们需要使用TypeToken来正确映射我们的实例。

版本2

经过上述解决方案，我想出了以下反序列化器：

class OneOrManyJsonDeserializer implements JsonDeserializer<List<?>> {

    @Override
    public List<?> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        final Type elementType = $Gson$Types.getCollectionElementType(typeOfT, List.class);

        if (json instanceof JsonArray) {
            final JsonArray array = (JsonArray) json;
            final int size = array.size();
            if (size == 0) {
                return Collections.emptyList();
            }

            final List<?> suites = new ArrayList<>(size);
            for (int i = 0; i < size; i++) {
                suites.add(context.deserialize(array.get(i), elementType));
            }

            return suites;
        }

        Object suite = context.deserialize(json, elementType);
        return Collections.singletonList(suite);
    }
}

我们不需要对其进行自定义。使用$Gson$Types类，我们可以获得元素的类型并反序列化内部元素。简单用法：

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonArray;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.annotations.SerializedName;
import com.google.gson.internal.$Gson$Types;

import java.io.File;
import java.io.FileReader;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class GsonApp {

    public static void main(String[] args) throws Exception {
        File jsonFile = new File("./resource/test.json").getAbsoluteFile();

        Gson gson = new GsonBuilder()
                .registerTypeAdapter(List.class, new OneOrManyJsonDeserializer())
                .setPrettyPrinting()
                .create();

        TestResponse response = gson.fromJson(new FileReader(jsonFile), TestResponse.class);
        System.out.println(response);
    }
}

上面的代码也应该为您工作。