diff --git a/native/Cargo.lock b/native/Cargo.lock
index 6892886..14b05cf 100644
--- a/native/Cargo.lock
+++ b/native/Cargo.lock
@@ -159,18 +159,16 @@ dependencies = [
 
 [[package]]
 name = "jni"
-version = "0.21.1"
+version = "0.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1a87aa2bb7d2af34197c04845522473242e1aa17c12f4935d5856491a7fb8c97"
+checksum = "c6df18c2e3db7e453d3c6ac5b3e9d5182664d28788126d39b91f2d1e22b017ec"
 dependencies = [
  "cesu8",
- "cfg-if",
  "combine",
  "jni-sys",
  "log",
  "thiserror",
  "walkdir",
- "windows-sys",
 ]
 
 [[package]]
@@ -402,69 +400,3 @@ name = "winapi-x86_64-pc-windows-gnu"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
-
-[[package]]
-name = "windows-sys"
-version = "0.45.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "75283be5efb2831d37ea142365f009c02ec203cd29a3ebecbc093d52315b66d0"
-dependencies = [
- "windows-targets",
-]
-
-[[package]]
-name = "windows-targets"
-version = "0.42.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8e5180c00cd44c9b1c88adb3693291f1cd93605ded80c250a75d472756b4d071"
-dependencies = [
- "windows_aarch64_gnullvm",
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_gnullvm",
- "windows_x86_64_msvc",
-]
-
-[[package]]
-name = "windows_aarch64_gnullvm"
-version = "0.42.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "597a5118570b68bc08d8d59125332c54f1ba9d9adeedeef5b99b02ba2b0698f8"
-
-[[package]]
-name = "windows_aarch64_msvc"
-version = "0.42.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e08e8864a60f06ef0d0ff4ba04124db8b0fb3be5776a5cd47641e942e58c4d43"
-
-[[package]]
-name = "windows_i686_gnu"
-version = "0.42.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c61d927d8da41da96a81f029489353e68739737d3beca43145c8afec9a31a84f"
-
-[[package]]
-name = "windows_i686_msvc"
-version = "0.42.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "44d840b6ec649f480a41c8d80f9c65108b92d89345dd94027bfe06ac444d1060"
-
-[[package]]
-name = "windows_x86_64_gnu"
-version = "0.42.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8de912b8b8feb55c064867cf047dda097f92d51efad5b491dfb98f6bbb70cb36"
-
-[[package]]
-name = "windows_x86_64_gnullvm"
-version = "0.42.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "26d41b46a36d453748aedef1486d5c7a85db22e56aff34643984ea85514e94a3"
-
-[[package]]
-name = "windows_x86_64_msvc"
-version = "0.42.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9aec5da331524158c6d1a4ac0ab1541149c0b9505fde06423b02f5ef0106b9f0"
diff --git a/native/chromium/Cargo.toml b/native/chromium/Cargo.toml
index fb15c33..ec6755f 100644
--- a/native/chromium/Cargo.toml
+++ b/native/chromium/Cargo.toml
@@ -9,7 +9,7 @@ crate-type = ["rlib"]
 [dependencies]
 chromium_jni_utils = { path = "../chromium_jni_utils/" }
 chromium_jni_macro = { path = "../chromium_jni_macro/" }
-jni = "0.21.1"
+jni = "0.19.0"
 winapi = { version = "0.3.9", features = ["winuser", "libloaderapi"] }
 
 [features]
diff --git a/native/chromium/build.rs b/native/chromium/build.rs
index 0f2282a..0e5596a 100644
--- a/native/chromium/build.rs
+++ b/native/chromium/build.rs
@@ -193,5 +193,4 @@ fn generator(cef_path: std::path::Display) -> bindgen::Builder {
         .raw_line("use jni::objects::GlobalRef;")
         .raw_line("use jni::objects::JObject;")
         .raw_line("use chromium_jni_utils::jni_unwrap;")
-        .raw_line("use std::ops::DerefMut;")
 }
diff --git a/native/chromium/src/cef/mod.rs b/native/chromium/src/cef/mod.rs
index 74fe0bb..b27eef7 100644
--- a/native/chromium/src/cef/mod.rs
+++ b/native/chromium/src/cef/mod.rs
@@ -16,7 +16,6 @@ use crate::ToJava;
 use jni::objects::GlobalRef;
 use jni::objects::JObject;
 use chromium_jni_utils::jni_unwrap;
-use std::ops::DerefMut;
 pub mod win;
 pub use self::win::_cef_window_info_t;
 pub use self::win::_cef_main_args_t;
diff --git a/native/chromium/src/cef/win.rs b/native/chromium/src/cef/win.rs
index e9e2e81..5ce464a 100644
--- a/native/chromium/src/cef/win.rs
+++ b/native/chromium/src/cef/win.rs
@@ -16,7 +16,6 @@ use crate::ToJava;
 use jni::objects::GlobalRef;
 use jni::objects::JObject;
 use chromium_jni_utils::jni_unwrap;
-use std::ops::DerefMut;
 use crate::cef::cef_string_t;
 
 pub type DWORD = ::std::os::raw::c_ulong;
diff --git a/native/chromium/src/lib.rs b/native/chromium/src/lib.rs
index 0db5e0a..84008ad 100644
--- a/native/chromium/src/lib.rs
+++ b/native/chromium/src/lib.rs
@@ -16,11 +16,7 @@ use jni::objects::JValue;
 use jni::JNIEnv;
 
 impl FromJavaMember for cef::cef_base_ref_counted_t {
-    fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
-        name: &str,
-    ) -> cef::cef_base_ref_counted_t {
+    fn from_java_member(env: JNIEnv, object: JObject, name: &str) -> cef::cef_base_ref_counted_t {
         let obj = env
             .get_field(
                 object,
@@ -30,114 +26,114 @@ impl FromJavaMember for cef::cef_base_ref_counted_t {
             .unwrap()
             .l()
             .unwrap();
-        FromJava::from_java(env, &obj)
+        FromJava::from_java(env, obj)
     }
 }
 
 /// Allows constructing an object from a Java object
 pub trait ToJava<'a> {
     /// Constructs `Self` from the JNI object `object`
-    fn to_java(_env: &JNIEnv<'a>, value: Self) -> JValue<'a, 'a>;
+    fn to_java(_env: JNIEnv<'a>, value: Self) -> JValue<'a>;
 }
 
 impl<'a, T> ToJava<'a> for *mut T {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Long(value as i64)
     }
 }
 impl<'a, T> ToJava<'a> for *const T {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Long(value as i64)
     }
 }
 
 impl<'a> ToJava<'a> for i32 {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(value)
     }
 }
 
 impl<'a> ToJava<'a> for usize {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Long(value.try_into().unwrap())
     }
 }
 impl<'a> ToJava<'a> for i64 {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Long(value)
     }
 }
 impl<'a> ToJava<'a> for f64 {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Double(value)
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_process_id_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 impl<'a> ToJava<'a> for cef::cef_cursor_type_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 impl<'a> ToJava<'a> for cef::cef_errorcode_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 impl<'a> ToJava<'a> for cef::cef_transition_type_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_window_open_disposition_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_log_severity_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_event_flags_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_termination_status_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_focus_source_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_jsdialog_type_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_quick_menu_edit_state_flags_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
 
 impl<'a> ToJava<'a> for cef::cef_preferences_type_t {
-    fn to_java(mut _env: &JNIEnv, value: Self) -> JValue<'a, 'a> {
+    fn to_java(_env: JNIEnv, value: Self) -> JValue<'a> {
         JValue::Int(unsafe { std::mem::transmute(value) })
     }
 }
diff --git a/native/chromium_jni/Cargo.toml b/native/chromium_jni/Cargo.toml
index 22a5dac..4d55095 100644
--- a/native/chromium_jni/Cargo.toml
+++ b/native/chromium_jni/Cargo.toml
@@ -4,7 +4,7 @@ version = "1.0.0"
 edition = "2021"
 
 [dependencies]
-jni = "0.21.1"
+jni = "0.19.0"
 chromium = { path = "../chromium/" }
 chromium_swt = { path = "../chromium_swt/" }
 chromium_jni_macro = { path = "../chromium_jni_macro/" }
diff --git a/native/chromium_jni/src/allocate.rs b/native/chromium_jni/src/allocate.rs
index d4d837d..741d70d 100644
--- a/native/chromium_jni/src/allocate.rs
+++ b/native/chromium_jni/src/allocate.rs
@@ -19,9 +19,9 @@ use jni::JNIEnv;
 macro_rules! jni_allocate {
     ($name:tt, $type:ty) => {
         #[jni_name($name, $type)]
-        pub extern "C" fn allocate(env: JNIEnv, _class: JClass, object: &JObject) -> jlong {
-            let global_ref = env.new_global_ref(object).unwrap();
-            let object: JNIWrapperType<$type> = JNICEFCallback::jni_allocate(env, global_ref);
+        pub extern "C" fn allocate(env: JNIEnv, _class: JClass, object: JObject) -> jlong {
+            let object: JNIWrapperType<$type> =
+                JNICEFCallback::jni_allocate(env, env.new_global_ref(object).unwrap());
             return Box::into_raw(Box::new(object)) as jlong;
         }
     };
@@ -32,7 +32,7 @@ macro_rules! jni_deallocate {
     ($name:tt, $type:ty) => {
         #[jni_name($name, $type)]
         pub extern "C" fn deallocate(
-            mut _env: JNIEnv,
+            _env: JNIEnv,
             _class: JClass,
             object: *mut chromium::cef::_cef_display_handler_t,
         ) {
diff --git a/native/chromium_jni/src/swt_wrapper.rs b/native/chromium_jni/src/swt_wrapper.rs
index 73403c6..da256d9 100644
--- a/native/chromium_jni/src/swt_wrapper.rs
+++ b/native/chromium_jni/src/swt_wrapper.rs
@@ -12,9 +12,9 @@ use jni::JNIEnv;
 
 #[no_mangle]
 pub extern "C" fn Java_org_eclipse_set_browser_lib_ChromiumLib_memmove__Lorg_eclipse_set_browser_lib_cef_1popup_1features_1t_2J(
-    mut env: JNIEnv,
+    env: JNIEnv,
     _class: JClass,
-    destination: &JObject,
+    destination: JObject,
     source: *mut chromium::cef::_cef_popup_features_t,
 ) {
     let source_object = unsafe { *source };
@@ -53,10 +53,10 @@ pub extern "C" fn Java_org_eclipse_set_browser_lib_ChromiumLib_memmove__Lorg_ecl
 
 #[no_mangle]
 pub extern "C" fn Java_org_eclipse_set_browser_lib_ChromiumLib_cefswt_1function_1id(
-    mut _env: JNIEnv,
+    _env: JNIEnv,
     _class: JClass,
     arg0: jlong,
-    arg1: &JObject,
+    arg1: JObject,
 ) {
     // IMPROVE: Avoid creating this object here
     let mut func_st = chromium_swt::FunctionSt {
diff --git a/native/chromium_jni_macro/src/derive_from_java_impl.rs b/native/chromium_jni_macro/src/derive_from_java_impl.rs
index a7f4293..8ae8f40 100644
--- a/native/chromium_jni_macro/src/derive_from_java_impl.rs
+++ b/native/chromium_jni_macro/src/derive_from_java_impl.rs
@@ -38,7 +38,7 @@ pub fn derive_from_java_impl(tokens: TokenStream) -> TokenStream {
 
     let modified = quote! {
         impl FromJava for #name {
-            fn from_java(env: &mut JNIEnv, object: &JObject) -> #name {
+            fn from_java(env: JNIEnv, object: JObject) -> #name {
                 return #name {
                     #(#query_parts, )*
                 };
diff --git a/native/chromium_jni_macro/src/jni_allocate.rs b/native/chromium_jni_macro/src/jni_allocate.rs
index 656cf31..f52de92 100644
--- a/native/chromium_jni_macro/src/jni_allocate.rs
+++ b/native/chromium_jni_macro/src/jni_allocate.rs
@@ -51,8 +51,8 @@ pub fn jni_allocate(tokens: TokenStream) -> TokenStream {
 
     let modified = quote! {
         impl JNICEFCallback for #name {
-            fn jni_allocate(mut env: JNIEnv, object: GlobalRef) -> chromium_jni_utils::JNIWrapperType<#name> {
-                let class = &env.get_object_class(object.as_obj()).unwrap();
+            fn jni_allocate(env: JNIEnv, object: GlobalRef) -> chromium_jni_utils::JNIWrapperType<#name> {
+                let class = env.get_object_class(object.as_obj()).unwrap();
                 
                 #(#jni_callbacks)*
 
@@ -92,7 +92,7 @@ fn build_initialization(
         let signature = jni_signature(field);
         
         quote! { #field_ident: match env.get_method_id(class, stringify!(#field_ident), #signature) {
-                Err(_e) => {
+                Err(e) => {
                     // Attempting to get the method id of a method that does not exists results 
                     // in a NoSuchMethodException. As we do not want to throw this, clear the exception 
                     env.exception_clear().unwrap();
@@ -140,8 +140,9 @@ fn build_jni_callback(
 
         let retline = match result {
             None => quote! {},
-            Some(_) => quote! { return chromium_jni_utils::FromJavaValue::from_java_value(&env, result); }
+            Some(_) => quote! { return chromium_jni_utils::FromJavaValue::from_java_value(env, result); }
         };
+        
         let func_ident = syn::Ident::new(&format!("jni_{}", field_ident), Span::call_site());
         
         let signature = jni_signature(field);
@@ -149,8 +150,8 @@ fn build_jni_callback(
             /// C-Callback which calls the Java function via JNI
             unsafe extern "C" fn #func_ident(#args) #result_tag {
                 let wrapper = jni_unwrap(self_);
-                let mut guard = (*wrapper).jvm.attach_current_thread().unwrap();
-                let env: &mut JNIEnv = guard.deref_mut();
+                let guard = (*wrapper).jvm.attach_current_thread().unwrap();
+                let env: JNIEnv = *guard;
                 let result = env.call_method((*wrapper).this.as_obj(), stringify!(#field_ident), #signature, &[#(#argnames, )*]).expect(stringify!(#func_ident));
                 #retline
             };
diff --git a/native/chromium_jni_macro/src/jni_wrap_impl.rs b/native/chromium_jni_macro/src/jni_wrap_impl.rs
index 4d9dad4..3bafec1 100644
--- a/native/chromium_jni_macro/src/jni_wrap_impl.rs
+++ b/native/chromium_jni_macro/src/jni_wrap_impl.rs
@@ -56,7 +56,7 @@ pub fn jni_wrap_attr_impl(attr: TokenStream, item: TokenStream) -> TokenStream {
     );
     let q = quote! {
         #[no_mangle]
-        pub unsafe extern fn #fname(mut _env: jni::JNIEnv, _class: jni::objects::JClass, #(#func_args, )*) #ret_expr {
+        pub extern fn #fname(_env: jni::JNIEnv, _class: jni::objects::JClass, #(#func_args, )*) #ret_expr {
             #(#param_prepare; )*
             #call_expr
             #(#param_cleanup; )*
@@ -88,7 +88,7 @@ fn setup_argument(
     };
     let arg = Ident::new(&format!("arg{}", index), Span::call_site());
     let param = Ident::new(&format!("param{}", index), Span::call_site());
-    let (arg_type, prepare, cleanup) = handle_arg(&arg, ty);
+    let (arg_type, prepare, cleanup) = handle_arg(&arg, &param, ty);
 
     (
         // JNI Function argument: arg[index]: type
@@ -110,11 +110,11 @@ fn handle_return(retn: &Option<String>) -> (proc_macro2::TokenStream, proc_macro
         Some(t) => match t.as_str() {
             "String" => (
                 quote! { -> jni::sys::jstring },
-                quote! { return _env.new_string(result).unwrap().into_raw(); },
+                quote! { return _env.new_string(result).unwrap().into_inner(); },
             ),
             "CStr" => (
                 quote! { -> jni::sys::jstring },
-                quote! { return _env.new_string(result.to_str().unwrap()).unwrap().into_raw(); },
+                quote! { return _env.new_string(result.to_str().unwrap()).unwrap().into_inner(); },
             ),
             "* mut c_char" | "* const c_char" => (
                 quote! { -> jni::sys::jstring },
@@ -123,7 +123,7 @@ fn handle_return(retn: &Option<String>) -> (proc_macro2::TokenStream, proc_macro
                         return std::ptr::null_mut();
                     }
                     let result = unsafe { CStr::from_ptr(result) };
-                    return _env.new_string(result.to_str().unwrap()).unwrap().into_raw();
+                    return _env.new_string(result.to_str().unwrap()).unwrap().into_inner();
                 },
             ),
             "cef :: cef_string_userfree_t" => (
@@ -131,7 +131,7 @@ fn handle_return(retn: &Option<String>) -> (proc_macro2::TokenStream, proc_macro
                 quote! {
                     let str: String = chromium::utils::str_from_cef(result);
                     unsafe { cef::cef_string_userfree_utf16_free(result) };
-                    return _env.new_string(str).unwrap().into_raw();
+                    return _env.new_string(str).unwrap().into_inner();
                 },
             ),
             "c_int" | "i32" => (
@@ -157,6 +157,7 @@ fn handle_return(retn: &Option<String>) -> (proc_macro2::TokenStream, proc_macro
 /// result is (paramType, mapping, cleanup)
 fn handle_arg(
     arg: &Ident,
+    param: &Ident,
     ty: &Type,
 ) -> (
     proc_macro2::TokenStream,
@@ -186,18 +187,20 @@ fn handle_arg(
             quote! {},
         ),
         "* const c_char" => (
-            quote! { &jni::objects::JString },
-            quote! { _env.get_string_unchecked(#arg).map(|strs| strs.into_raw()).unwrap_or(std::ptr::null_mut()) },
-            quote! {},
+            quote! { jni::objects::JString },
+            quote! { _env.get_string_utf_chars(#arg).unwrap_or(std::ptr::null_mut()) },
+            quote! { if !#param.is_null() {
+                _env.release_string_utf_chars(#arg, #param).unwrap()
+            }},
         ),
         "Option < Vec < u8 > >" => (
-            quote! { jni::objects::JByteArray },
-            quote! { _env.convert_byte_array(&#arg).map(|arr| Some(arr)).unwrap_or(None) },
+            quote! { jni::sys::jbyteArray },
+            quote! { _env.convert_byte_array(#arg).map(|arr| Some(arr)).unwrap_or(None) },
             quote! {},
         ),
         "Vec < u8 >" => (
-            quote! { jni::objects::JByteArray },
-            quote! { _env.convert_byte_array(&#arg).unwrap() },
+            quote! { jni::sys::jbyteArray },
+            quote! { _env.convert_byte_array(#arg).unwrap() },
             quote! {},
         ),
         _ => {
diff --git a/native/chromium_jni_utils/Cargo.toml b/native/chromium_jni_utils/Cargo.toml
index 402e519..bddee1a 100644
--- a/native/chromium_jni_utils/Cargo.toml
+++ b/native/chromium_jni_utils/Cargo.toml
@@ -4,7 +4,7 @@ version = "1.0.0"
 edition = "2021"
 
 [dependencies]
-jni = "0.21.1"
+jni = "0.19.0"
 
 [lib]
 crate-type = ["rlib"]
diff --git a/native/chromium_jni_utils/src/lib.rs b/native/chromium_jni_utils/src/lib.rs
index 2858bfb..96ee42a 100644
--- a/native/chromium_jni_utils/src/lib.rs
+++ b/native/chromium_jni_utils/src/lib.rs
@@ -8,7 +8,7 @@
  */
 use jni::objects::GlobalRef;
 use jni::objects::JObject;
-use jni::objects::JValueGen;
+use jni::objects::JValue;
 use jni::JNIEnv;
 use jni::JavaVM;
 
@@ -36,54 +36,54 @@ pub trait JNICEFCallback {
 /// Allows extracting an object from a Java field
 pub trait FromJavaMember {
     /// Constructs `Self` from the field `name` in the JNI object `object`
-    fn from_java_member(env: &mut JNIEnv, object: &JObject, name: &str) -> Self;
+    fn from_java_member(env: JNIEnv, object: JObject, name: &str) -> Self;
 }
 
 /// Allows constructing an object from a Java object
 pub trait FromJava {
     /// Constructs `Self` from the JNI object `object`
-    fn from_java(env: &mut JNIEnv, object: &JObject) -> Self;
+    fn from_java(env: JNIEnv, object: JObject) -> Self;
 }
 
 /// Allows constructing an object from a Java object
 pub trait FromJavaValue {
     /// Constructs `Self` from the JNI object `object`
-    fn from_java_value<O>(env: &JNIEnv, object: JValueGen<O>) -> Self;
+    fn from_java_value(env: JNIEnv, object: JValue) -> Self;
 }
 
 impl FromJavaValue for i32 {
-    fn from_java_value<O>(mut _env: &JNIEnv, object: JValueGen<O>) -> Self {
+    fn from_java_value(_env: JNIEnv, object: JValue) -> Self {
         match object {
-            JValueGen::Int(i) => i,
-            JValueGen::Byte(b) => b.into(),
-            JValueGen::Short(b) => b.into(),
-            JValueGen::Bool(b) => b.into(),
+            JValue::Int(i) => i,
+            JValue::Byte(b) => b.into(),
+            JValue::Short(b) => b.into(),
+            JValue::Bool(b) => b.into(),
             _ => panic!("Wrong type for from_java_value"),
         }
     }
 }
 
 impl FromJavaValue for i64 {
-    fn from_java_value<O>(mut _env: &JNIEnv, object: JValueGen<O>) -> Self {
+    fn from_java_value(_env: JNIEnv, object: JValue) -> Self {
         match object {
-            JValueGen::Long(l) => l,
-            JValueGen::Int(i) => i.into(),
-            JValueGen::Byte(b) => b.into(),
-            JValueGen::Short(b) => b.into(),
-            JValueGen::Bool(b) => b.into(),
+            JValue::Long(l) => l,
+            JValue::Int(i) => i.into(),
+            JValue::Byte(b) => b.into(),
+            JValue::Short(b) => b.into(),
+            JValue::Bool(b) => b.into(),
             _ => panic!("Wrong type for from_java_value"),
         }
     }
 }
 
 impl<T> FromJavaValue for *mut T {
-    fn from_java_value<O>(mut _env: &JNIEnv, object: JValueGen<O>) -> Self {
+    fn from_java_value(_env: JNIEnv, object: JValue) -> Self {
         object.j().unwrap() as *mut T
     }
 }
 
 impl FromJavaMember for usize {
-    fn from_java_member(env: &mut JNIEnv, object: &JObject, name: &str) -> usize {
+    fn from_java_member(env: JNIEnv, object: JObject, name: &str) -> usize {
         // Read an integer field
         return env
             .get_field(object, name, "I")
@@ -96,8 +96,8 @@ impl FromJavaMember for usize {
 // IMPROVE: Is there a better way to generalize across an arbitrary number of function args
 impl<T, U> FromJavaMember for Option<unsafe extern "C" fn(T) -> U> {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T) -> U> {
         let field_value = env
@@ -113,8 +113,8 @@ impl<T, U> FromJavaMember for Option<unsafe extern "C" fn(T) -> U> {
 
 impl<T, U, V> FromJavaMember for Option<unsafe extern "C" fn(T, V) -> U> {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V) -> U> {
         let field_value = env
@@ -130,8 +130,8 @@ impl<T, U, V> FromJavaMember for Option<unsafe extern "C" fn(T, V) -> U> {
 
 impl<T, U, V, W> FromJavaMember for Option<unsafe extern "C" fn(T, V, W) -> U> {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W) -> U> {
         let field_value = env
@@ -147,8 +147,8 @@ impl<T, U, V, W> FromJavaMember for Option<unsafe extern "C" fn(T, V, W) -> U> {
 
 impl<T, U, V, W, Q> FromJavaMember for Option<unsafe extern "C" fn(T, V, W, Q) -> U> {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q) -> U> {
         let field_value = env
@@ -164,8 +164,8 @@ impl<T, U, V, W, Q> FromJavaMember for Option<unsafe extern "C" fn(T, V, W, Q) -
 
 impl<T, U, V, W, Q, R> FromJavaMember for Option<unsafe extern "C" fn(T, V, W, Q, R) -> U> {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R) -> U> {
         let field_value = env
@@ -181,8 +181,8 @@ impl<T, U, V, W, Q, R> FromJavaMember for Option<unsafe extern "C" fn(T, V, W, Q
 
 impl<T, U, V, W, Q, R, S> FromJavaMember for Option<unsafe extern "C" fn(T, V, W, Q, R, S) -> U> {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R, S) -> U> {
         let field_value = env
@@ -200,8 +200,8 @@ impl<T, U, V, W, Q, R, S, A> FromJavaMember
     for Option<unsafe extern "C" fn(T, V, W, Q, R, S, A) -> U>
 {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R, S, A) -> U> {
         let field_value = env
@@ -219,8 +219,8 @@ impl<T, U, V, W, Q, R, S, A, B> FromJavaMember
     for Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B) -> U>
 {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B) -> U> {
         let field_value = env
@@ -238,8 +238,8 @@ impl<T, U, V, W, Q, R, S, A, B, C> FromJavaMember
     for Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C) -> U>
 {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C) -> U> {
         let field_value = env
@@ -257,8 +257,8 @@ impl<T, U, V, W, Q, R, S, A, B, C, D> FromJavaMember
     for Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C, D) -> U>
 {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C, D) -> U> {
         let field_value = env
@@ -276,8 +276,8 @@ impl<T, U, V, W, Q, R, S, A, B, C, D, E> FromJavaMember
     for Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C, D, E) -> U>
 {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C, D, E) -> U> {
         let field_value = env
@@ -295,8 +295,8 @@ impl<T, U, V, W, Q, R, S, A, B, C, D, E, F> FromJavaMember
     for Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C, D, E, F) -> U>
 {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C, D, E, F) -> U> {
         let field_value = env
@@ -314,8 +314,8 @@ impl<T, U, V, W, Q, R, S, A, B, C, D, E, F, G> FromJavaMember
     for Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C, D, E, F, G) -> U>
 {
     fn from_java_member(
-        env: &mut JNIEnv,
-        object: &JObject,
+        env: JNIEnv,
+        object: JObject,
         name: &str,
     ) -> Option<unsafe extern "C" fn(T, V, W, Q, R, S, A, B, C, D, E, F, G) -> U> {
         let field_value = env
diff --git a/native/chromium_swt/Cargo.toml b/native/chromium_swt/Cargo.toml
index 143374a..e3b609c 100644
--- a/native/chromium_swt/Cargo.toml
+++ b/native/chromium_swt/Cargo.toml
@@ -10,7 +10,7 @@ crate-type = ["rlib"]
 path = "src/lib.rs"
 
 [dependencies]
-jni = "0.21.1"
+jni = "0.19.0"
 chromium = { path = "../chromium/" }
 chromium_subp = { path = "../chromium_subp/" }
 chromium_jni_macro = { path = "../chromium_jni_macro/" }
diff --git a/native/chromium_swt/src/cef_cookie.rs b/native/chromium_swt/src/cef_cookie.rs
index a2332f5..69b815e 100644
--- a/native/chromium_swt/src/cef_cookie.rs
+++ b/native/chromium_swt/src/cef_cookie.rs
@@ -20,7 +20,10 @@ pub extern "C" fn Java_org_eclipse_set_browser_lib_cefswt_1cookie_1visitor_1t_ce
     cookie: *mut chromium::cef::_cef_cookie_t,
 ) -> jstring {
     let value = unsafe { CStr::from_ptr(cefswt_cookie_value(cookie)) };
-    return env.new_string(value.to_str().unwrap()).unwrap().into_raw();
+    return env
+        .new_string(value.to_str().unwrap())
+        .unwrap()
+        .into_inner();
 }
 
 #[no_mangle]
@@ -30,7 +33,10 @@ pub extern "C" fn Java_org_eclipse_set_browser_lib_cefswt_1cookie_1visitor_1t_ce
     cookie: *mut chromium::cef::_cef_cookie_t,
 ) -> jstring {
     let value = unsafe { CStr::from_ptr(cefswt_cookie_to_java(cookie)) };
-    return env.new_string(value.to_str().unwrap()).unwrap().into_raw();
+    return env
+        .new_string(value.to_str().unwrap())
+        .unwrap()
+        .into_inner();
 }
 
 fn cefswt_cookie_to_java(cookie: *mut chromium::cef::_cef_cookie_t) -> *mut c_char {
diff --git a/native/chromium_swt/src/cef_download_item.rs b/native/chromium_swt/src/cef_download_item.rs
index a20edfe..6c4514d 100644
--- a/native/chromium_swt/src/cef_download_item.rs
+++ b/native/chromium_swt/src/cef_download_item.rs
@@ -24,12 +24,15 @@ pub unsafe extern "C" fn get_full_path(
     let path = (*item).get_full_path.unwrap()(item);
 
     let value = CStr::from_ptr(crate::cefswt_cefstring_to_java(path));
-    return env.new_string(value.to_str().unwrap()).unwrap().into_raw();
+    return env
+        .new_string(value.to_str().unwrap())
+        .unwrap()
+        .into_inner();
 }
 
 #[jni_name("org.eclipse.set.browser.lib.cef_download_item_t")]
 pub unsafe extern "C" fn is_cancelled(
-    mut _env: JNIEnv,
+    _env: JNIEnv,
     _class: JClass,
     item: *mut chromium::cef::_cef_download_item_t,
 ) -> jboolean {
@@ -38,7 +41,7 @@ pub unsafe extern "C" fn is_cancelled(
 
 #[jni_name("org.eclipse.set.browser.lib.cef_download_item_t")]
 pub unsafe extern "C" fn is_complete(
-    mut _env: JNIEnv,
+    _env: JNIEnv,
     _class: JClass,
     item: *mut chromium::cef::_cef_download_item_t,
 ) -> jboolean {
@@ -53,25 +56,27 @@ pub unsafe extern "C" fn get_url(
 ) -> jstring {
     let url = (*item).get_url.unwrap()(item);
     let value = CStr::from_ptr(crate::cefswt_cefstring_to_java(url));
-    return env.new_string(value.to_str().unwrap()).unwrap().into_raw();
+    return env
+        .new_string(value.to_str().unwrap())
+        .unwrap()
+        .into_inner();
 }
 
 #[jni_name("org.eclipse.set.browser.lib.cef_download_item_t")]
 pub unsafe extern "C" fn before_download_callback(
-    mut _env: JNIEnv,
+    _env: JNIEnv,
     _class: JClass,
     callback: *mut chromium::cef::_cef_before_download_callback_t,
     jpath: JString,
 ) {
-    let rpath = _env.get_string_unchecked(&jpath);
+    let rpath = _env
+        .get_string_utf_chars(jpath)
+        .unwrap_or(std::ptr::null_mut());
 
-    let strs = match rpath {
-        Ok(value) => value.into_raw(),
-        Err(_e) => std::ptr::null_mut(),
-    };
-
-    let path = chromium::utils::cef_string_from_c(strs);
+    let path = chromium::utils::cef_string_from_c(rpath);
     (*callback).cont.unwrap()(callback, &path, 0);
+
+    _env.release_string_utf_chars(jpath, rpath).unwrap();
 }
 
 #[jni_wrapper("org.eclipse.set.browser.lib.cef_download_item_t")]
diff --git a/native/chromium_swt/src/lib.rs b/native/chromium_swt/src/lib.rs
index 09910e3..ca7c2c7 100644
--- a/native/chromium_swt/src/lib.rs
+++ b/native/chromium_swt/src/lib.rs
@@ -14,7 +14,6 @@
 extern crate chromium;
 use chromium::cef;
 use chromium_jni_macro::{jni_name, jni_wrapper};
-use jni::objects::JString;
 
 mod app;
 pub mod cef_browser;
@@ -308,16 +307,19 @@ pub fn cefswt_set_intptr(ptr: *mut ::std::os::raw::c_int, value: c_int) {
 
 #[jni_name("org.eclipse.set.browser.lib.ChromiumLib")]
 #[no_mangle]
-pub extern "C" fn cefswt_cstring_to_java<'local>(
-    mut _env: jni::JNIEnv<'local>,
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub extern "C" fn cefswt_cstring_to_java(
+    _env: jni::JNIEnv,
     _class: jni::objects::JClass,
     string: *const c_char,
-) -> JString<'local> {
+) -> jni::sys::jstring {
     if string.is_null() {
-        return jni::objects::JObject::null().into();
+        return std::ptr::null_mut();
     }
     let string = unsafe { CStr::from_ptr(string) };
-    _env.new_string(string.to_str().unwrap()).unwrap()
+    _env.new_string(string.to_str().unwrap())
+        .unwrap()
+        .into_inner()
 }
 
 #[jni_wrapper("org.eclipse.set.browser.lib.ChromiumLib")]