Require pre-parsed JNI signatures

JNI signatures are now expected to be pre-parsed into a MethodSignature
or FieldSignature before being used to make method calls or get/set
fields.

In the common case the `jni_sig!()` macro can be used to parse a JNI
signature at compile time and emit the appropriate `*Signature` struct.

In the unlikely case that a signature needs to be parsed at runtime then
`RuntimeMethodSignature/RuntimeFieldSignature::from_str` can be used
and it's then possible to borrow a `MethodSignature` or `FieldSignature`
from these runtime structs.

Author: rib

jni-macros/src/bind_java_type.rs

@@ -2044,7 +2044,6 @@ fn generate_id_fields_and_inits(
 
         // Create CStr literals for both the name and signature
         let name_cstr = lit_cstr_mutf8(java_name);
-        let sig_cstr = lit_cstr_mutf8(signature);
 
         // Add field to API struct
         fields.push(quote! {
@@ -2053,7 +2052,7 @@ fn generate_id_fields_and_inits(
 
         // Add initialization
         inits.push(quote! {
-            #field_name: env.#lookup_fn(class, #jni::strings::JNIStr::from_cstr_unchecked(#name_cstr), #jni::strings::JNIStr::from_cstr_unchecked(#sig_cstr))?,
+            #field_name: env.#lookup_fn(class, #jni::strings::JNIStr::from_cstr_unchecked(#name_cstr), #jni::jni_sig!(jni=#jni, #signature))?,
         });
     }
 
@@ -3918,7 +3917,6 @@ fn generate_native_registration_code(
 
         // Create CStr literals for name and signature
         let name_cstr = lit_cstr_mutf8(java_name);
-        let sig_cstr = lit_cstr_mutf8(&jni_signature);
 
         // Always use the generated wrapper function (even for raw_fn)
         // This ensures type checking and allows exports to work
@@ -3928,7 +3926,7 @@ fn generate_native_registration_code(
         native_method_descriptors.push(quote! {
             #jni::NativeMethod {
                 name: #jni::strings::JNIStr::from_cstr_unchecked(#name_cstr),
-                sig: #jni::strings::JNIStr::from_cstr_unchecked(#sig_cstr),
+                sig: #jni::jni_sig!(jni=#jni, #jni_signature),
                 fn_ptr: #fn_ptr,
             }
         });

src/descriptors/exception_desc.rs

@@ -3,6 +3,7 @@ use crate::{
     env::Env,
     errors::*,
     objects::{Auto, IntoAuto as _, JClass, JObject, JString, JThrowable, JValue},
+    signature::{JavaType, MethodSignature, Primitive},
     strings::{JNIStr, JNIString},
 };
 
@@ -17,8 +18,16 @@ where
 
     fn lookup(self, env: &mut Env<'local>) -> Result<Self::Output> {
         let jmsg = JString::from_jni_str(env, self.1.as_ref())?.auto();
-        let obj: JObject =
-            env.new_object(self.0, c"(Ljava/lang/String;)V", &[JValue::from(&jmsg)])?;
+        let ctor_args = &[JavaType::Object];
+        // Safety: We are sure the arguments and return type are consistent with the signature string.
+        let ctor_sig = unsafe {
+            MethodSignature::from_raw_parts(
+                JNIStr::from_cstr(c"(Ljava/lang/String;)V"),
+                ctor_args,
+                JavaType::Primitive(Primitive::Void),
+            )
+        };
+        let obj: JObject = env.new_object(self.0, &ctor_sig, &[JValue::from(&jmsg)])?;
         let throwable = env.cast_local::<JThrowable>(obj)?;
         Ok(throwable.auto())
     }

src/descriptors/field_desc.rs

@@ -3,14 +3,15 @@ use crate::{
     env::Env,
     errors::*,
     objects::{JClass, JFieldID, JStaticFieldID},
+    signature::FieldSignature,
     strings::JNIStr,
 };
 
-unsafe impl<'local, 'other_local, T, U, V> Desc<'local, JFieldID> for (T, U, V)
+unsafe impl<'local, 'other_local, 'sig, T, U, V> Desc<'local, JFieldID> for (T, U, V)
 where
     T: Desc<'local, JClass<'other_local>>,
     U: AsRef<JNIStr>,
-    V: AsRef<JNIStr>,
+    V: AsRef<FieldSignature<'sig>>,
 {
     type Output = JFieldID;
 
@@ -19,11 +20,11 @@ where
     }
 }
 
-unsafe impl<'local, 'other_local, T, U, V> Desc<'local, JStaticFieldID> for (T, U, V)
+unsafe impl<'local, 'other_local, 'sig, T, U, V> Desc<'local, JStaticFieldID> for (T, U, V)
 where
     T: Desc<'local, JClass<'other_local>>,
     U: AsRef<JNIStr>,
-    V: AsRef<JNIStr>,
+    V: AsRef<FieldSignature<'sig>>,
 {
     type Output = JStaticFieldID;
 

src/descriptors/method_desc.rs

@@ -3,14 +3,15 @@ use crate::{
     env::Env,
     errors::*,
     objects::{JClass, JMethodID, JStaticMethodID},
+    signature::MethodSignature,
     strings::JNIStr,
 };
 
-unsafe impl<'local, 'other_local, T, U, V> Desc<'local, JMethodID> for (T, U, V)
+unsafe impl<'local, 'other_local, 'sig, 'sig_args, T, U, V> Desc<'local, JMethodID> for (T, U, V)
 where
     T: Desc<'local, JClass<'other_local>>,
     U: AsRef<JNIStr>,
-    V: AsRef<JNIStr>,
+    V: AsRef<MethodSignature<'sig, 'sig_args>>,
 {
     type Output = JMethodID;
 
@@ -19,10 +20,11 @@ where
     }
 }
 
-unsafe impl<'local, 'other_local, T, Signature> Desc<'local, JMethodID> for (T, Signature)
+unsafe impl<'local, 'other_local, 'sig, 'sig_args, T, Signature> Desc<'local, JMethodID>
+    for (T, Signature)
 where
     T: Desc<'local, JClass<'other_local>>,
-    Signature: AsRef<JNIStr>,
+    Signature: AsRef<MethodSignature<'sig, 'sig_args>>,
 {
     type Output = JMethodID;
 
@@ -31,11 +33,12 @@ where
     }
 }
 
-unsafe impl<'local, 'other_local, T, U, V> Desc<'local, JStaticMethodID> for (T, U, V)
+unsafe impl<'local, 'other_local, 'sig, 'sig_args, T, U, V> Desc<'local, JStaticMethodID>
+    for (T, U, V)
 where
     T: Desc<'local, JClass<'other_local>>,
     U: AsRef<JNIStr>,
-    V: AsRef<JNIStr>,
+    V: AsRef<MethodSignature<'sig, 'sig_args>>,
 {
     type Output = JStaticMethodID;