基于C++模板函数与Fluent API设计的JNI反射库，极大的简化JNI反射调用。
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弱化数据类型概念，强化操作意图
在执行中间任何操作的时候无需关心数据类型，内部会依据传入的参数签名自动调用对应数据类型的原JNI函数，只需要在最终进行get操作与set操作时通过泛型指定数据类型
在执行中间操作时只需关注操作意图，即：
- 对什么操作：on
- 操作什么：构造函数用construct，域用field，静态域用staicField，函数调用用call，静态函数调用用staticCall
- 最终目的：获取值用get，修改值用set
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基于OOD设计的Fluent API：
int intField = Reflect::on(env, object).field("intField", "I").get<jint>(); // 获取Filed Reflect::on(env, object).field("intField", "I").set<jint>(1); // 设置Field jobject object = Reflect::on(env, "tech/huqi/jnioor/Sample").construct("()V").get<jobject>(); // 调用构造函数 jstring content = Reflect::on(env, object).call("toString"，"()Ljava/lang/String;").get<jstring>(); // 调用toString函数 -
完善的判空与异常检测逻辑
当执行JNI函数的GetFieldID，GetMethodID，CallXxxMethod，CallStaticXxxMethod调用时，如果获取的域，方法，调用的方法不存在时会抛出异常导致程序奔溃
这在对一些非官方系统(如非安卓原生，java原生)的类进行JNI调用时很常见，比如Xposed检测，如果你的代码运行在一个未安装Xposed框架的机器上，那么关于Xposed的域，方法操作都会出现异常导致崩溃。所以一个健壮稳定的JNI调用一般类似这样：
jclass jcls_Sample = env->FindClass("tech/huqi/jnioor/Sample"); if (jcls_Sample != NULL) { jmethodID jmid_init = env->GetMethodID(jcls_Sample, "<init>", "()V"); if (jmid_init != NULL) { jobject job_Sample = env->NewObject(jcls_Sample, jmid_init); if (job_Sample != NULL) { jfieldID jfid_intField = env->GetFieldID(jcls_Sample, "intField", "I"); if (jfid_intField != NULL) { int intField = env->GetIntField(job_Sample, jfid_intField); // ...... 省略后续其他逻辑 } else { checkAndClearException(env);// 检测并清理异常 } } else { checkAndClearException(env);// 检测并清理异常 } } else { checkAndClearException(env);// 检测并清理异常 } } else { checkAndClearException(env);// 检测并清理异常 } env->DeleteLocalRef(jcls_Sample); // 释放局部引用即对三方框架的类进行JNI调用时进行判空或异常检测后再进行下一步操作，如果为空进行异常检测并清理，如果中间产生了一些临时局部引用，还需要释放局部引用。但这样做代码结构嵌套太深，不利于阅读与后期维护，虽然这种嵌套可以采用goto语句来避免
现在有了这个库，只需要这样就包含了上述代码的功能：
jobject object = Reflect::on(env, "tech/huqi/jnioor/Sample").construct("()V").get<jobject>(); if(object!=NULL){ int intField = Reflect::on(env, object).field("intField", "I").get<jint>(); }
（以下示例基于文档最后的Sample类进行操作）
// 获取非态域
int intField = Reflect::on(env, object).field("intField", "I").get<jint>();
long longField = Reflect::on(env, object).field("longField", "J").get<jlong>();
float floatField = Reflect::on(env, object).field("floatField", "F").get<jfloat>();
double doubleField = Reflect::on(env, object).field("doubleField", "D").get<jdouble>();
jstring stringField = Reflect::on(env, object).field("stringField",
"Ljava/lang/String;").get<jstring>();
// 获取静态域
int staticIntField = Reflect::on(env, clazz).staticField("staticIntField",
"I").get<jint>();
long staticLongField = Reflect::on(env, clazz).staticField("staticLongField",
"J").get<jlong>();
float staticFloatField = Reflect::on(env, clazz).staticField("staticFloatField",
"F").get<jfloat>();
double staticDoubleField = Reflect::on(env, clazz).staticField("staticDoubleField",
"D").get<jdouble>();
jstring staticStringField = Reflect::on(env, clazz).staticField("staticStringField",
"Ljava/lang/String;").get<jstring>();
// 设置非静态域
Reflect::on(env, object).field("intField", "I").set<jint>(1);
Reflect::on(env, object).field("longField", "J").set<jlong>(1);
Reflect::on(env, object).field("floatField", "F").set<jfloat>(1.0f);
Reflect::on(env, object).field("doubleField", "D").set<jdouble>(1.0);
Reflect::on(env, object).field("stringField", "Ljava/lang/String;").set<jobject>(
env->NewStringUTF("modify stringField value"));
// 设置静态域
Reflect::on(env, clazz).staticField("staticIntField", "I").set<jint>(1);
Reflect::on(env, clazz).staticField("staticLongField", "J").set<jlong>(1);
Reflect::on(env, clazz).staticField("staticFloatField", "F").set<jfloat>(1.0f);
Reflect::on(env, clazz).staticField("staticDoubleField", "D").set<jdouble>(1.0);
Reflect::on(env, clazz).staticField("staticStringField","Ljava/lang/String;").set<jobject>(
env->NewStringUTF("modify staticStringField value"));
// 调用构造函数
jobject object = Reflect::on(env, clazz).construct("()V").get<jobject>();
// 调用函数
jstring content = Reflect::on(env, object).call("toString"，"()Ljava/lang/String;").get<jstring>();
public class Sample {
private static final String TAG = "JniReflectSample";
private int intField = 0;
private static int staticIntField = 0;
private long longField = 0;
private static long staticLongField = 0;
private float floatField = 0.1f;
private static float staticFloatField = 0.1f;
private double doubleField = 0.1;
private static double staticDoubleField = 0.1;
private String stringField = "this is a non-static String";
private static String staticStringField = "this is a static String";
public static native void nativePrint();
public int getIntField() {
return intField;
}
public long getLongField() {
return longField;
}
public float getFloatField() {
return floatField;
}
public double getDoubleField() {
return doubleField;
}
public String getStringField() {
return stringField;
}
@Override
public String toString() {
return "Sample{" +
"intField=" + intField +
", longField=" + longField +
", floatField=" + floatField +
", doubleField=" + doubleField +
", stringField='" + stringField + '\'' +
", staticIntField=" + staticIntField +
", staticLongField=" + staticLongField +
", staticFloatField=" + staticFloatField +
", staticDoubleField=" + staticDoubleField +
", staticStringField='" + staticStringField + '\'' +
'}';
}
}
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