ParameterizedType和isAssignableFrom

最新推荐文章于 2021-12-31 18:25:40 发布
转载 最新推荐文章于 2021-12-31 18:25:40 发布 · 748 阅读 · 0

本文介绍了如何在Java运行时获取泛型的具体类型，通过分析Gson源码并提供了一个具体的实现示例。

学过Java的人都知道,Java的泛型是编译时实现的,运行时泛型信息是被擦除的.但是我们为了解析Json数组就必须知道应该为给定的Class的List类型解析出什么样类型的对象以赋值.这个问题看上去是不可解决的了.但是因为我的接口设计是仿照Gson的,而Gson是可以实现这个功能的.带着疑问,我在Gson的代码中找到了这个.

<code class="language-Java hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;">  <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ParameterizedTypeImpl</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ParameterizedType</span>, <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Serializable</span> {</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> Type ownerType;
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> Type rawType;
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> Type[] typeArguments;

    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">ParameterizedTypeImpl</span>(Type ownerType, Type rawType, Type... typeArguments) {
      <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// require an owner type if the raw type needs it</span>
      <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (rawType <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">instanceof</span> Class<?>) {
        Class<?> rawTypeAsClass = (Class<?>) rawType;
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> isStaticOrTopLevelClass = Modifier.isStatic(rawTypeAsClass.getModifiers())
            || rawTypeAsClass.getEnclosingClass() == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>;
        checkArgument(ownerType != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> || isStaticOrTopLevelClass);
      }

      <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.ownerType = ownerType == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> ? <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span> : canonicalize(ownerType);
      <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.rawType = canonicalize(rawType);
      <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.typeArguments = typeArguments.clone();
      <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> t = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; t < <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.typeArguments.length; t++) {
        checkNotNull(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.typeArguments[t]);
        checkNotPrimitive(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.typeArguments[t]);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.typeArguments[t] = canonicalize(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.typeArguments[t]);
      }
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li></ul>

事实上ParameterizedType就是我们需要寻找的带泛型的类啦.但是上面这段代码由于是在Gson的类型系统设计下,所以显得不是那么好懂.我搜索了其中的关键字后,在JPJson中实现了下面的代码.

<code class="language-Java hljs actionscript has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;">Class fieldType = field.getType();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (fieldType.isAssignableFrom(List.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span>)) {
    ParameterizedType pt = <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>;
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
        pt = (ParameterizedType) field.getGenericType();
    } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (ClassCastException e) {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RuntimeException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"you must offer a genericType on the bean's list type for json array to parse"</span>);
    }
    Class cla = (Class) pt.getActualTypeArguments()[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>];
    fieldType = cla;
                    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

上面这段代码中

  • 首先我使用field.getType()获取了给定Class参数的类型.
  • 然后使用fieldType.isAssignableFrom(List.class)判断该field是否是一个List.
  • 如果是List类型,下面关键的来了,我使用field.getGenericType()获取带泛型的List类型
  • 然后将其强转为ParameterizedType类型.
  • 这里要捕获一个类型强转的异常,因为如果对应的List没有填写泛型类型的话,那么这次的强转会出异常.这个异常是由于用户提供的泛型类没有带泛型类型导致的,而我们确实需要这个类型.所以我们重新抛出一个新的吟唱并且带上必要的提示信息.
  • ParameterizedType是包含了泛型的Field类型所以实际上它应该是java.util.List<java.lang.String>这种形式的类型.所以我们使用Class cla = (Class) pt.getActualTypeArguments()[0]这个方法来获取真正的泛型类型.

下次各位读者需要获取泛型的类型的话,就可以使用这种方法哦.

运行时获取泛型的原理

这里摘抄一段来自书上的话,这是我之前看这本书是看到过的,书上只是提供了原理,但是没说在代码中应该怎么使用,今天使用过后,算是对原理有了更深的理解.

由于泛型的引入,各种场景(虚拟机解析,反射等)下的方法调用都可能会对原有的基础产生影响和新的需求,如在泛型类中如何获取传入的参数化类型等.因此JCP组织对虚拟机规范做出了相应的修改,引入了诸如Signature,LocalVariableTypeTable等新的属性用于解决伴随泛型而来的参数类型识别问题,Signature是其中最重要的一项属性,它的作用就是存储一个方法在字节码层面的特征签名,这个属性中保存的参数类型不是原生类型而是包括了参数化类型的信息.修改后的虚拟机规范要求所有能识别49.0以上版本的Class文件虚拟机都要能正确识别Signature参数.

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06-25
- 泛型类型检查（`ParameterizedType` 和元素类型验证） - 动态创建安全集合（避免 NPE） ### 典型应用场景： - **数据反序列化后**：将 JSON 解析出的"骨架对象"替换为内存中的实际对象 - **数据同步时**：合并...
package com.example.kucun2.entity.data; import android.content.Context; import android.os.Handler; import android.os.Looper; import android.util.Log; import com.example.kucun2.entity.*; import com.example.kucun2.function.MyAppFnction; import com.example.kucun2.function.SafeLogger; import com.google.gson.Gson; import com.google.gson.reflect.TypeToken; import java.io.IOException; import java.lang.reflect.Field; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; import java.util.*; import okhttp3.Call; import okhttp3.Callback; import okhttp3.OkHttpClient; import okhttp3.Request; import okhttp3.Response; public class Data { // 数据集合声明（保持原有属性名不变） public static SynchronizedList<Bancai> bancais = new SynchronizedList<>(Bancai.class); public static SynchronizedList<Caizhi> caizhis = new SynchronizedList<>(Caizhi.class); public static SynchronizedList<Mupi> mupis = new SynchronizedList<>(Mupi.class); public static SynchronizedList<Chanpin> chanpins = new SynchronizedList<>(Chanpin.class); public static SynchronizedList<Chanpin_Zujian> chanpin_zujians = new SynchronizedList<>(Chanpin_Zujian.class); public static SynchronizedList<Dingdan> dingdans = new SynchronizedList<>(Dingdan.class); public static SynchronizedList<Dingdan_Chanpin> dingdan_chanpins = new SynchronizedList<>(Dingdan_Chanpin.class); public static SynchronizedList<Dingdan_chanpin_zujian> Dingdan_chanpin_zujians = new SynchronizedList<>(Dingdan_chanpin_zujian.class); public static SynchronizedList<Kucun> kucuns = new SynchronizedList<>(Kucun.class); public static SynchronizedList<Zujian> zujians = new SynchronizedList<>(Zujian.class); public static SynchronizedList<User> users = new SynchronizedList<>(User.class); public static SynchronizedList<Jinhuo> jinhuos = new SynchronizedList<>(Jinhuo.class); public static final Map<Class,SynchronizedList<SynchronizableEntity>> dataCollectionMap=new HashMap<>(); private static final Gson gson = new Gson(); private static OkHttpClient client ; private static final String TAG = "DataLoader"; static { // 静态初始化块：在类加载时执行，保证所有静态字段已初始化 try { Field[] fields = Data.class.getDeclaredFields(); for (Field field : fields) { if (SynchronizedList.class.isAssignableFrom(field.getType())) { // 获取泛型类型参数 ParameterizedType parameterizedType = (ParameterizedType) field.getGenericType(); Class<?> entityType = (Class<?>) parameterizedType.getActualTypeArguments()[0]; // 创建 SynchronizedList 并设置实体类型 SynchronizedList<?> list = new SynchronizedList<>((Class<SynchronizableEntity>) entityType); field.set(null, list); // 将列表添加到 dataCollectionMap if (list != null) { dataCollectionMap.put(entityType, (SynchronizedList<SynchronizableEntity>) list); } } } } catch (IllegalAccessException e) { throw new RuntimeException("初始化dataCollectionMap失败", e); } } public static void loadAllData(Context context, LoadDataCallback callback) { if (Looper.myLooper() != Looper.getMainLooper()) { throw new IllegalStateException("Data.loadAllData must be called on main thread"); } // 确保使用安全的客户端 if (client == null) { client= MyAppFnction.getClient(); } //禁用同步 SynchronizableEntity.setSyncEnabled(false); String url = MyAppFnction.getStringResource("string", "url") + MyAppFnction.getStringResource("string", "url_all"); Log.d("url", "loadAllData: " + url); Request request = new Request.Builder() .url(url) .build(); client.newCall(request).enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { Log.e(TAG, "Failed to load data", e); SynchronizableEntity.setSyncEnabled(true); if (callback != null)safeCallback(callback, false); } @Override public void onResponse(Call call, Response response) throws IOException { if (!response.isSuccessful()) { Log.e(TAG, "Unexpected response code: " + response.code()); if (callback != null) safeCallback(callback, false); return; } String responseData = response.body().string(); SynchronizableEntity.setSyncEnabled(true); ensurePreservedObjects(); parseAndAssignData(responseData, context, callback); } }); } // 解析并赋值数据 private static void parseAndAssignData(String jsonData, Context context, LoadDataCallback callback) { // 创建包含所有数据类型的TypeToken ensurePreservedObjects(); Type informationType = new TypeToken<Information<AllDataResponse>>(){}.getType(); Information<AllDataResponse> information = gson.fromJson(jsonData, informationType); Log.e(TAG, "Invalid response data"+jsonData); if (information == null || information.getData() == null || information.getStatus() != 200) { Log.e(TAG, "Invalid response data"); if (callback != null) callback.onFailure(); return; } AllDataResponse allData = information.getData(); SafeLogger.d("data","数据："+gson.toJson(allData)); safeInitializeList(allData.bancais); safeInitializeList(allData.caizhis); safeInitializeList(allData.mupis); safeInitializeList(allData.chanpins); safeInitializeList(allData.chanpin_zujians); safeInitializeList(allData.dingdans); safeInitializeList(allData.dingdan_chanpins); safeInitializeList(allData.Dingdan_chanpin_zujians); safeInitializeList(allData.kucuns); safeInitializeList(allData.zujians); safeInitializeList(allData.users); safeInitializeList(allData.jinhuos); SafeLogger.d("data","数据：非空"+gson.toJson(allData)); // 赋值到对应的列表（使用安全方法保持已有引用） updateList(bancais, allData.bancais); updateList(caizhis, allData.caizhis); updateList(mupis, allData.mupis); updateList(chanpins, allData.chanpins); updateList(chanpin_zujians, allData.chanpin_zujians); updateList(dingdans, allData.dingdans); updateList(dingdan_chanpins, allData.dingdan_chanpins); updateList(Dingdan_chanpin_zujians, allData.Dingdan_chanpin_zujians); updateList(kucuns, allData.kucuns); updateList(zujians, allData.zujians); updateList(users, allData.users); updateList(jinhuos, allData.jinhuos); SafeLogger.d("data","数据：data.bancais"+gson.toJson(Data.bancais)); // 在设置引用关系前关闭同步 SynchronizableEntity.setSyncEnabled(false); Log.d("DataParse", "开始解析JSON数据"); resolveReferences(); Log.d("DataParse", "解析完成，实体关系建立"); // 为所有实体设置正确状态（已存在服务器） setAllEntitiesState(SynchronizableEntity.SyncState.MODIFIED); ensurePreservedObjects(); // 启用同步 SynchronizableEntity.setSyncEnabled(true); if (callback != null) callback.onSuccess(); } public static void safeCallback(LoadDataCallback callback, boolean success) { new Handler(Looper.getMainLooper()).post(() -> { if (success) { callback.onSuccess(); } else { callback.onFailure(); } }); } // 更新列表内容但保持对象引用不变 private static <T extends SynchronizableEntity> void updateList(List<T> existingList, List<T> newList) { if (newList == null) return; // 创建临时列表保留预置对象 List<T> preservedObjects = new ArrayList<>(); for (T item : existingList) { if (item != null && item.isPreservedObject()) { preservedObjects.add(item); } } // 清除原有列表并添加保留对象 existingList.clear(); existingList.addAll(preservedObjects); // 添加新数据，跳过预置对象的ID for (T newItem : newList) { if (newItem.getId() != null && newItem.getId() != -1) { existingList.add(newItem); } } } // 添加确保预置对象存在的方法 private static void ensurePreservedObjects() { if (!containsPreservedObject(bancais)) bancais.add(createInstance(Bancai.class)); if (!containsPreservedObject(caizhis)) caizhis.add(createInstance(Caizhi.class)); if (!containsPreservedObject(mupis)) mupis.add(createInstance(Mupi.class)); if (!containsPreservedObject(chanpins)) chanpins.add(createInstance(Chanpin.class)); if (!containsPreservedObject(chanpin_zujians)) chanpin_zujians.add(createInstance(Chanpin_Zujian.class)); if (!containsPreservedObject(dingdans)) dingdans.add(createInstance(Dingdan.class)); if (!containsPreservedObject(kucuns)) kucuns.add(createInstance(Kucun.class)); if (!containsPreservedObject(zujians)) zujians.add(createInstance(Zujian.class)); if (!containsPreservedObject(Dingdan_chanpin_zujians)) Dingdan_chanpin_zujians.add(createInstance(Dingdan_chanpin_zujian.class)); if (!containsPreservedObject(dingdan_chanpins)) dingdan_chanpins.add(createInstance(Dingdan_Chanpin.class)); if (!containsPreservedObject(jinhuos)) jinhuos.add(createInstance(Jinhuo.class)); if (!containsPreservedObject(users)) users.add(createInstance(User.class)); // 为其他需要预置对象的列表添加... try { setDefaultAssociation(bancais); } catch (IllegalAccessException e) { throw new RuntimeException(e); } catch (ClassNotFoundException e) { throw new RuntimeException(e); } } // 检查列表是否包含预置对象 private static <T extends SynchronizableEntity> boolean containsPreservedObject(List<T> list) { for (T item : list) { if (item != null && item.isPreservedObject()) { Log.d(TAG, "containsPreservedObject: "+item.getId()); item= (T) createInstance(item.getClass()); return true; } } return !list.isEmpty(); } private static <T extends SynchronizableEntity> void setDefaultAssociation(SynchronizedList<T> e ) throws IllegalAccessException, ClassNotFoundException { for (T t:e) { Class clazz=t.getClass(); Field[] fields = clazz.getDeclaredFields(); for (Field f:fields){ f.setAccessible(true); Class s=f.getType(); if(SynchronizableEntity.class.isAssignableFrom(s)){ if (t.getId()<0 ||f.get(t)==null|| ((SynchronizableEntity)f.get(t)).getId()==null) { f.set(t, dataCollectionMap.get(s).get(-1)); }else { f.set(t, dataCollectionMap.get(s).get( ((SynchronizableEntity)f.get(t)).getId())); } } if (List.class.isAssignableFrom(s)){ Type genericSuperclass = s.getGenericSuperclass(); if (genericSuperclass instanceof ParameterizedType) { ParameterizedType pt = (ParameterizedType) genericSuperclass; Type[] types = pt.getActualTypeArguments(); System.out.println("集合类型: " + types[0].getTypeName()); // User Class c=Class.forName(types[0].getTypeName()); if(SynchronizableEntity.class.isAssignableFrom(c)) { List<SynchronizableEntity> l = (List<SynchronizableEntity>) f.get(t); if (l == null) { l = new ArrayList(); } if (l.isEmpty() || t.getId() < 0) { l.add(dataCollectionMap.get(c).get(-1)); } if (!l.isEmpty()) { for (int i = 0; i < l.size(); i++) { l.set(i,dataCollectionMap.get(c).get( l.get(i).getId())); } } } } } } } } /** * 根据传入的Class对象创建对应类型的实例 * @param clazz 目标类型对应的Class对象 * @param <T> 目标类型泛型参数 * @return 指定类型的实例 */ public static <T> T createInstance(Class<T> clazz) { try { // 通过反射调用无参构造函数创建实例 T g=clazz.getDeclaredConstructor().newInstance(); // Log.d("g",""+g); Field[] fields = clazz.getDeclaredFields(); for (Field f: fields ) { f.setAccessible(true); if(f.getType().equals(String.class)){ f.set(g,"无"); } if(f.getType().equals(Integer.class)){ f.set(g,-1); }if(f.getType().equals(Double.class)){ f.set(g,-1.0); } if (f.getType().equals(Date.class)){ f.set(g,new Date()); } } Log.d("g",""+gson.toJson(g)); clazz.getMethod("setId",Integer.class).invoke(g,-1); clazz.getMethod("setState", SynchronizableEntity. SyncState.class) .invoke(g,SynchronizableEntity.SyncState.PRESERVED); return g; } catch (Exception e) { Log.d(TAG, "createInstance: "+e.getLocalizedMessage()); throw new RuntimeException("创建实例失败: " + clazz.getName(), e); } } // // 创建预置板材对象 // private static<T> T createPreservedBancai(Class<T> t) { // Bancai preserved = new Bancai(); // preserved.setId(-1); // preserved.setState(SynchronizableEntity.SyncState.PRESERVED); // return preserved; // } // 解析对象间的引用关系（使用ID关联） private static void resolveReferences() { // 创建ID到对象的映射 Map<Integer, Bancai> bancaiMap = createIdMap(bancais); Map<Integer, Caizhi> caizhiMap = createIdMap(caizhis); Map<Integer, Mupi> mupiMap = createIdMap(mupis); Map<Integer, Chanpin> chanpinMap = createIdMap(chanpins); Map<Integer, Zujian> zujianMap = createIdMap(zujians); Map<Integer, Dingdan> dingdanMap = createIdMap(dingdans); Map<Integer, Kucun> kucunMap = createIdMap(kucuns); Log.d("RefResolution", "开始解析实体关系..."); // 解析Bancai引用 for (Bancai bancai : bancais) { if (bancai.getCaizhi() != null) { bancai.setCaizhi(caizhiMap.get(bancai.getCaizhi().getId())); } if (bancai.getMupi1() != null) { bancai.setMupi1(mupiMap.get(bancai.getMupi1().getId())); } if (bancai.getMupi2() != null) { bancai.setMupi2(mupiMap.get(bancai.getMupi2().getId())); } } // 解析Kucun引用 for (Kucun kucun : kucuns) { if(kucun==null)break; if (kucun.getBancai() != null) { kucun.setBancai(bancaiMap.get(kucun.getBancai().getId())); } } // 解析订单相关的嵌套对象 for (Dingdan_Chanpin dc : dingdan_chanpins) { if(dc==null)break; if (dc.getDingdan() != null) { dc.setDingdan(dingdanMap.get(dc.getDingdan().getId())); } if (dc.getChanpin() != null) { dc.setChanpin(chanpinMap.get(dc.getChanpin().getId())); } } // 解析产品相关的嵌套对象 for (Chanpin_Zujian cz : chanpin_zujians) { if(cz==null)break; if (cz.getChanpin() != null) { cz.setChanpin(chanpinMap.get(cz.getChanpin().getId())); } if (cz.getZujian() != null) { cz.setZujian(zujianMap.get(cz.getZujian().getId())); } if (cz.getBancai() != null) { cz.setBancai(bancaiMap.get(cz.getBancai().getId())); } } // 解析库存关联 for (Kucun k : kucuns) { if(k==null)break; if (k.getBancai() != null) { k.setBancai(bancaiMap.get(k.getBancai().getId())); } } // 添加缺失的实体关系解析 for (Dingdan_chanpin_zujian dm : Dingdan_chanpin_zujians) { if (dm.getZujian() != null) { // 确保组件和板材关联 dm.setZujian(chanpin_zujians.stream() .filter(cz -> cz.getId().equals(dm.getZujian().getId())) .findFirst().orElse(null)); if (dm.getBancai() != null) { dm.setBancai(bancais.stream() .filter(b -> b.getId().equals(dm.getBancai().getId())) .findFirst().orElse(null)); } } } } // 创建ID到对象的映射 private static <T extends EntityClassGrassrootsid> Map<Integer, T> createIdMap(List<T> list) { return createSafeIdMap(list); } // 回调接口 public interface LoadDataCallback { void onSuccess(); void onFailure(); } // 确保列表不为null private static <T> void safeInitializeList(List<T> list) { if (list == null) { list = new ArrayList<>(); } } // 安全创建ID映射 private static <T extends EntityClassGrassrootsid> Map<Integer, T> createSafeIdMap(List<T> list) { Map<Integer, T> map = new HashMap<>(); if (list != null) { for (T item : safeIterable(list)) { if (item != null && item.getId() != null) { map.put(item.getId(), item); } } } return map; } // 安全迭代方法（处理空集合） private static <T> Iterable<T> safeIterable(List<T> list) { return list != null ? list : Collections.emptyList(); } // 内部类用于解析JSON响应 public static class AllDataResponse { public List<Bancai> bancais; public List<Caizhi> caizhis; public List<Mupi> mupis; public List<Chanpin> chanpins; public List<Chanpin_Zujian> chanpin_zujians; public List<Dingdan> dingdans; public List<Dingdan_Chanpin> dingdan_chanpins; public List<Dingdan_chanpin_zujian> Dingdan_chanpin_zujians; public List<Kucun> kucuns; public List<Zujian> zujians; public List<User> users; public List<Jinhuo> jinhuos; } // 新增方法：设置所有实体状态 private static void setAllEntitiesState(SynchronizableEntity.SyncState state) { setListState(bancais, state); setListState(caizhis, state); setListState(mupis, state); setListState(Dingdan_chanpin_zujians, state); setListState(dingdans, state); setListState(chanpins, state); setListState(chanpin_zujians, state); setListState(zujians, state); setListState(jinhuos, state); setListState(kucuns, state); setListState(users, state); setListState(caizhis, state); // ... 其他列表 } private static <T extends SynchronizableEntity> void setListState(List<T> list, SynchronizableEntity.SyncState state) { for (T entity : list) { entity.setState(state); } } } E FATAL EXCEPTION: main Process: com.example.kucun2, PID: 21888 java.lang.ExceptionInInitializerError at com.example.kucun2.MainActivity.loadAppData(MainActivity.java:100) at com.example.kucun2.MainActivity.onCreate(MainActivity.java:31) at android.app.Activity.performCreate(Activity.java:9441) at android.app.Activity.performCreate(Activity.java:9387) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1526) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4644) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4876) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:112) at android.app.servertransaction.TransactionExecutor.executeNonLifecycleItem(TransactionExecutor.java:220) at android.app.servertransaction.TransactionExecutor.executeTransactionItems(TransactionExecutor.java:148) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:120) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:3102) at android.os.Handler.dispatchMessage(Handler.java:109) at android.os.Looper.loopOnce(Looper.java:250) at android.os.Looper.loop(Looper.java:340) at android.app.ActivityThread.main(ActivityThread.java:9913) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:621) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:957) Caused by: java.lang.IllegalArgumentException: Entity type cannot be null at com.example.kucun2.entity.data.SynchronizedList.<init>(SynchronizedList.java:35) at com.example.kucun2.entity.data.Data.<clinit>(Data.java:26) ... 19 more
06-13
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