摘要：對于如果以修改源碼的方式，也可以通過判斷當前的數據類型是否與預期的數據類型一致的方式進行。但由于每種數據類型都是一個匿名內部類，很難通過判斷預期的數據類型是啥，所以可以通過添加捕獲異常，在發生異常后，跳過解析。
一、項目地址
項目地址：github-gson-plugin
二、Gson解析核心類
1.ArrayTypeAdapter.JAVA 用于解析數組類型的數據
public Object read(JsonReader in) throws IOException {
if(in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
} else {
List list = new ArrayList();
in.beginArray();
Object array;
while(in.hasNext()) {
array = this.componentTypeAdapter.read(in);
list.add(array);
}
in.endArray();
array = Array.newInstance(this.componentType, list.size());
for(int i = 0; i < list.size(); ++i) {
Array.set(array, i, list.get(i));
}
return array;
}
}
2.CollectionTypeAdapterFactory.JAVA 用于解析集合類型的數據
@Override public Collection read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
}
Collection collection = constructor.construct();
in.beginArray();
while (in.hasNext()) {
E instance = elementTypeAdapter.read(in);
collection.add(instance);
}
in.endArray();
return collection;
}
3.MapTypeAdapterFactory.JAVA 用于解析map類型的數據
@Override public Map read(JsonReader in) throws IOException {
JsonToken peek = in.peek();
if (peek == JsonToken.NULL) {
in.nextNull();
return null;
}
Map map = constructor.construct();
if (peek == JsonToken.BEGIN_ARRAY) {
in.beginArray();
while (in.hasNext()) {
in.beginArray(); // entry array
K key = keyTypeAdapter.read(in);
V value = valueTypeAdapter.read(in);
V replaced = map.put(key, value);
if (replaced != null) {
throw new JsonSyntaxException("duplicate key: " + key);
}
in.endArray();
}
in.endArray();
} else {
in.beginObject();
while (in.hasNext()) {
JsonReaderInternalAccess.INSTANCE.promoteNameToValue(in);
K key = keyTypeAdapter.read(in);
V value = valueTypeAdapter.read(in);
V replaced = map.put(key, value);
if (replaced != null) {
throw new JsonSyntaxException("duplicate key: " + key);
}
}
in.endObject();
}
return map;
}
4.ReflectiveTypeAdapterFactory.JAVA 用于解析Object類型
@Override public T read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
}
T instance = constructor.construct();
try {
in.beginObject();
while (in.hasNext()) {
String name = in.nextName();
BoundField field = boundFields.get(name);
if (field == null || !field.deserialized) {
in.skipValue();
} else {
field.read(in, instance);
}
}
} catch (IllegalStateException e) {
throw new JsonSyntaxException(e);
} catch (IllegalAccessException e) {
throw new AssertionError(e);
}
in.endObject();
return instance;
}
5.TypeAdapters.JAVA 用于解析基本數據類型
里邊每種基本數據類型，都對應一個匿名內部類，只列出boolean類型的解析，其它省略
public static final TypeAdapter BOOLEAN = new TypeAdapter() {
@Override
public Boolean read(JsonReader in) throws IOException {
JsonToken peek = in.peek();
if (peek == JsonToken.NULL) {
in.nextNull();
return null;
} else if (peek == JsonToken.STRING) {
// support strings for compatibility with GSON 1.7
return Boolean.parseBoolean(in.nextString());
}
return in.nextBoolean();
}
@Override
public void write(JsonWriter out, Boolean value) throws IOException {
out.value(value);
}
};
三、跳過異常字段
1.對于ArrayTypeAdapter.JAVA，CollectionTypeAdapterFactory.JAVA，MapTypeAdapterFactory.JAVA，ReflectiveTypeAdapterFactory.JAVA 我們很清楚的知道預期的數據類型是啥，所以可以判斷當前的數據類型是否與預期的數據類型一致，如果不一致則跳過解析。
2.對于TypeAdapters.JAVA 如果以修改源碼的方式，也可以通過判斷當前的數據類型是否與預期的數據類型一致的方式進行。但由于每種數據類型都是一個匿名內部類，很難通過javassist判斷預期的數據類型是啥，所以可以通過添加try-catch捕獲異常，在發生異常后，跳過解析。
3.判斷數據類型是否與預期的數據類型一致，如果不一致則跳過解析。
/**
* used for array、collection、map、object
* skipValue when expected token error
*
* @param in input json reader
* @param expectedToken expected token
*/
public static boolean checkJsonToken(JsonReader in, JsonToken expectedToken) {
if (in == null || expectedToken == null) {
return false;
}
JsonToken inToken = null;
try {
inToken = in.peek();
} catch (IOException e) {
e.printStackTrace();
}
if (inToken == expectedToken) {
return true;
}
if (inToken != JsonToken.NULL) {
String exception = "expected " + expectedToken + " but was " + inToken + " path " + in.getPath();
notifyJsonSyntaxError(exception);
}
skipValue(in);
return false;
}
1.方法入參：輸入的json為JsonReader，期望的數據類型為JsonToken
2.期望的數據類型：在調用方法的時候傳入
3.當前的數據類型：通過in.peek()獲取
4.當前字段：通過in.getPath()獲取
5.異常信息拼接：
String exception = "expected " + expectedToken + " but was " + inToken + " path " + in.getPath();
ReaderTools.JAVA源碼
四、GsonPlugin插件編寫
/**
* Created by tangfuling on 2018/10/25.
*/
class GsonPlugin implements Plugin {
@Override
void apply(Project project) {
//add dependencies
project.dependencies.add("compile",
"com.ke.gson.sdk:gson_sdk:1.3.0")
//add transform
project.android.registerTransform(new GsonJarTransform(project))
}
}
五、Transform侵入編譯流程
/**
* Created by tangfuling on 2018/10/25.
*/
class GsonJarTransform extends Transform {
private Project mProject
GsonJarTransform(Project project) {
mProject = project
}
@Override
String getName() {
return "GsonJarTransform"
}
@Override
Set getInputTypes() {
return TransformManager.CONTENT_CLASS
}
@Override
Set getScopes() {
return TransformManager.SCOPE_FULL_PROJECT
}
@Override
boolean isIncremental() {
return false
}
@Override
void transform(TransformInvocation transformInvocation)
throws TransformException, InterruptedException, IOException {
//初始化ClassPool
MyClassPool.resetClassPool(mProject, transformInvocation)
//處理jar和file
TransformOutputProvider outputProvider = transformInvocation.getOutputProvider()
for (TransformInput input : transformInvocation.getInputs()) {
for (JarInput jarInput : input.getJarInputs()) {
// name must be unique，or throw exception "multiple dex files define"
def jarName = jarInput.name
if (jarName.endsWith(".jar")) {
jarName = jarName.substring(0, jarName.length() - 4)
}
def md5Name = DigestUtils.md5Hex(jarInput.file.getAbsolutePath())
//source file
File file = InjectGsonJar.inject(jarInput.file, transformInvocation.context, mProject)
if (file == null) {
file = jarInput.file
}
//dest file
File dest = outputProvider.getContentLocation(jarName + md5Name,
jarInput.contentTypes, jarInput.scopes, Format.JAR)
FileUtils.copyFile(file, dest)
}
for (DirectoryInput directoryInput : input.getDirectoryInputs()) {
File dest = outputProvider.getContentLocation(directoryInput.name,
directoryInput.contentTypes, directoryInput.scopes, Format.DIRECTORY)
FileUtils.copyDirectory(directoryInput.file, dest)
}
}
}
}
六、javassist修改Gson字節碼
修改ArrayTypeAdapter.JAVA的read()方法
/**
* Created by tangfuling on 2018/10/30.
*/
public class InjectArrayTypeAdapter {
public static void inject(String dirPath) {
ClassPool classPool = MyClassPool.getClassPool()
File dir = new File(dirPath)
if (dir.isDirectory()) {
dir.eachFileRecurse { File file ->
if ("ArrayTypeAdapter.class".equals(file.name)) {
CtClass ctClass = classPool.getCtClass("com.google.gson.internal.bind.ArrayTypeAdapter")
CtMethod ctMethod = ctClass.getDeclaredMethod("read")
ctMethod.insertBefore(" if (!com.ke.gson.sdk.ReaderTools.checkJsonToken($1, com.google.gson.stream.JsonToken.BEGIN_ARRAY)) {
" +
" return null;
" +
" }")
ctClass.writeFile(dirPath)
ctClass.detach()
println("GsonPlugin: inject ArrayTypeAdapter success")
}
}
}
}
}
七、目錄
1.gson-plugin告別Json數據類型不一致（一）
2.gson-plugin基礎源碼分析（二）
3.gson-plugin深入源碼分析（三）
4.gson-plugin如何在JitPack發布（四）
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