Merge pull request #15955 from parthiv39731/BAEL-7426
BAEL-7426, Gson TypeToken with Dynamic ArrayList Item Type
This commit is contained in:
davidmartinezbarua
GitHub
commit
80bc3342ff
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@ -18,6 +18,11 @@
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<artifactId>gson</artifactId>
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<version>${gson.version}</version>
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</dependency>
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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<version>${guava.version}</version>
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</dependency>
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</dependencies>
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<properties>
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@ -0,0 +1,34 @@
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package com.baeldung.gson.jsontolist.type;
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import java.lang.reflect.ParameterizedType;
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import java.lang.reflect.Type;
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public class ParameterizedTypeImpl implements ParameterizedType {
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private final Class<?> rawType;
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private final Type[] actualTypeArguments;
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private ParameterizedTypeImpl(Class<?> rawType, Type[] actualTypeArguments) {
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this.rawType = rawType;
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this.actualTypeArguments = actualTypeArguments;
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}
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public static ParameterizedType make(Class<?> rawType, Type ... actualTypeArguments) {
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return new ParameterizedTypeImpl(rawType, actualTypeArguments);
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}
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@Override
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public Type[] getActualTypeArguments() {
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return actualTypeArguments;
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}
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@Override
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public Type getRawType() {
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return rawType;
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}
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@Override
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public Type getOwnerType() {
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return null;
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}
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}
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@ -0,0 +1,23 @@
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package com.baeldung.gson.jsontolist.type;
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public class School {
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private String name;
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private String city;
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public String getCity() {
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return city;
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}
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public void setCity(String city) {
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this.city = city;
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}
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}
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@ -0,0 +1,23 @@
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package com.baeldung.gson.jsontolist.type;
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public class Student {
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private String name;
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private String grade;
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public String getGrade() {
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return grade;
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}
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public void setGrade(String grade) {
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this.grade = grade;
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}
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}
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@ -0,0 +1,129 @@
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package com.baeldung.gson.jsontolist.type;
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import java.lang.reflect.Type;
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import java.util.ArrayList;
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import java.util.List;
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import static org.junit.jupiter.api.Assertions.*;
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import org.junit.jupiter.api.Test;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import com.google.common.reflect.TypeParameter;
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import com.google.gson.Gson;
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import com.google.gson.JsonArray;
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import com.google.gson.JsonElement;
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import com.google.gson.reflect.TypeToken;
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public class JsonArrayStringToListUnitTest {
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Logger LOGGER = LoggerFactory.getLogger(JsonArrayStringToListUnitTest.class);
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final String jsonArrayOfStudents =
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"["
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+ "{\"name\":\"John\", \"grade\":\"1\"}, "
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+ "{\"name\":\"Tom\", \"grade\":\"2\"}, "
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+ "{\"name\":\"Ram\", \"grade\":\"3\"}, "
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+ "{\"name\":\"Sara\", \"grade\":\"1\"}"
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+ "]";
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final String jsonArrayOfSchools =
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"["
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+ "{\"name\":\"St. John\", \"city\":\"Chicago City\"}, "
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+ "{\"name\":\"St. Tom\", \"city\":\"New York City\"}, "
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+ "{\"name\":\"St. Ram\", \"city\":\"Mumbai\"}, "
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+ "{\"name\":\"St. Sara\", \"city\":\"Budapest\"}"
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+ "]";
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@Test
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void givenJsonArray_whenListElementTypeDynamic_thenConvertToJavaListUsingTypeToken() {
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Gson gson = new Gson();
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TypeToken<List<Student>> typeTokenForListOfStudents = new TypeToken<List<Student>>(){};
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TypeToken<List<School>> typeTokenForListOfSchools = new TypeToken<List<School>>(){};
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List<Student> studentsLst = gson.fromJson(jsonArrayOfStudents, typeTokenForListOfStudents.getType());
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List<School> schoolLst = gson.fromJson(jsonArrayOfSchools, typeTokenForListOfSchools.getType());
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assertAll(
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() -> studentsLst.forEach(e -> assertTrue(e instanceof Student)),
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() -> schoolLst.forEach(e -> assertTrue(e instanceof School))
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);
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}
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@Test
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void givenJsonArray_whenListElementTypeDynamic_thenConvertToJavaListUsingTypeTokenFails() {
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Gson gson = new Gson();
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List<Student> studentsLst = gson.fromJson(jsonArrayOfStudents, new ListWithDynamicTypeElement<Student>().getType());
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assertFalse(studentsLst.get(0) instanceof Student);
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assertThrows(ClassCastException.class, () -> studentsLst.forEach(e -> assertTrue(e instanceof Student)));
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}
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class ListWithDynamicTypeElement<T> {
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Type getType() {
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TypeToken<List<T>> typeToken = new TypeToken<List<T>>(){};
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return typeToken.getType();
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}
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}
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@Test
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void givenJsonArray_whenListElementTypeDynamic_thenConvertToJavaListUsingGetParameterized() {
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Gson gson = new Gson();
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List<Student> studentsLst = gson.fromJson(jsonArrayOfStudents, getGenericTypeForListFromTypeTokenUsingGetParameterized(Student.class));
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List<School> schoolLst = gson.fromJson(jsonArrayOfSchools, getGenericTypeForListFromTypeTokenUsingGetParameterized(School.class));
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assertAll(
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() -> studentsLst.forEach(e -> assertTrue(e instanceof Student)),
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() -> schoolLst.forEach(e -> assertTrue(e instanceof School))
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);
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}
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@Test
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void givenJsonArray_whenListElementTypeDynamic_thenConvertToJavaListUsingJsonArray() {
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List<Student> studentsLst = createListFromJsonArray(jsonArrayOfStudents, Student.class);
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List<School> schoolLst = createListFromJsonArray(jsonArrayOfSchools, School.class);
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assertAll(
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() -> studentsLst.forEach(e -> assertTrue(e instanceof Student)),
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() -> schoolLst.forEach(e -> assertTrue(e instanceof School))
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);
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}
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@Test
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void givenJsonArray_whenListElementTypeDynamic_thenConvertToJavaListUsingTypeTokenFromGuava() {
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Gson gson = new Gson();
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List<Student> studentsLst = gson.fromJson(jsonArrayOfStudents, getTypeForListUsingTypeTokenFromGuava(Student.class));
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List<School> schoolLst = gson.fromJson(jsonArrayOfSchools, getTypeForListUsingTypeTokenFromGuava(School.class));
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assertAll(
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() -> studentsLst.forEach(e -> assertTrue(e instanceof Student)),
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() -> schoolLst.forEach(e -> assertTrue(e instanceof School))
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);
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}
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@Test
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void givenJsonArray_whenListElementTypeDynamic_thenConvertToJavaListUsingParameterizedType() {
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Gson gson = new Gson();
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List<Student> studentsLst = gson.fromJson(jsonArrayOfStudents, ParameterizedTypeImpl.make(List.class, Student.class));
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List<School> schoolLst = gson.fromJson(jsonArrayOfSchools, ParameterizedTypeImpl.make(List.class, School.class));
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assertAll(
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() -> studentsLst.forEach(e -> assertTrue(e instanceof Student)),
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() -> schoolLst.forEach(e -> assertTrue(e instanceof School))
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);
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}
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Type getGenericTypeForListFromTypeTokenUsingGetParameterized(Class elementClass) {
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return TypeToken.getParameterized(List.class, elementClass).getType();
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}
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<T> List<T> createListFromJsonArray(String jsonArray, Type elementType) {
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Gson gson = new Gson();
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List<T> list = new ArrayList<>();
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JsonArray array = gson.fromJson(jsonArray, JsonArray.class);
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for(JsonElement element : array) {
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T item = gson.fromJson(element, elementType);
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list.add(item);
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}
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return list;
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}
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<T> Type getTypeForListUsingTypeTokenFromGuava(Class<T> type) {
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return new com.google.common.reflect.TypeToken<List<T>>() {}
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.where(new TypeParameter<T>() {}, type)
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.getType();
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}
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}
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