JS调用C++函数抛出异常及捕捉异常详解
目录
总结
本文讲述如何利用v8::TryCatch捕捉js代码中发生的异常。
首先，声明TryCatch对象。
v8::TryCatch trycatch( isolate );
然后，定义抛出异常的函数：
void ThrowException( const v8::FunctionCallbackInfo<v8::Value>& info ) {
v8::Isolate* isolate = info.GetIsolate();
v8::HandleScope scope( isolate );
v8::Local<v8::Value> exc = v8::Local<v8::Value>::New( info.GetIsolate(),
v8::Exception::Error( v8::String::NewFromUtf8( isolate, "throw an exception" ).ToLocalChecked() ) );
info.GetIsolate()->ThrowException( exc );
}
设置访问器访问C++函数：
v8::Local<v8::ObjectTemplate> global = v8::ObjectTemplate::New( isolate );
global->Set( isolate, "throwException",
v8::FunctionTemplate::New( isolate, ThrowException ) );
因为异常发生在执行js文件期间，所以需要在Run函数后判断是否有异常发生。这里Run的结果没有继续调用ToLocalChecked()，因为result为NULL。
// Run the script to get the result.
v8::MaybeLocal<v8::Value> result = script->Run( context );
if ( trycatch.HasCaught() ) {
v8::Local<v8::Message> message = trycatch.Message();
ResolveMessage( message );
return -1;
}
这样就可以在js文件中使用C++函数抛出异常，并解析异常信息。
main.cpp
// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "include/libplatform/libplatform.h"
#include "include/v8.h"
#include "point.h"
using namespace std;
using namespace v8;
const std::string fileName = "file.js";
// Reads a file into a v8 string.
MaybeLocal<String> ReadFile( Isolate* isolate, const string& name ) {
FILE* file = fopen( name.c_str(), "rb" );
if ( file == NULL ) return MaybeLocal<String>();
fseek( file, 0, SEEK_END );
size_t size = ftell( file );
rewind( file );
std::unique_ptr<char> chars( new char[size + 1] );
chars.get()[size] = '\0';
for ( size_t i = 0; i < size;) {
i += fread( &chars.get()[i], 1, size - i, file );
if ( ferror( file ) ) {
fclose( file );
return MaybeLocal<String>();
}
}
fclose( file );
MaybeLocal<String> result = String::NewFromUtf8(
isolate, chars.get(), NewStringType::kNormal, static_cast<int>(size) );
return result;
}
void ThrowException( const v8::FunctionCallbackInfo<v8::Value>& info ) {
v8::Isolate* isolate = info.GetIsolate();
v8::HandleScope scope( isolate );
v8::Local<v8::Value> exc = v8::Local<v8::Value>::New( info.GetIsolate(),
v8::Exception::Error( v8::String::NewFromUtf8( isolate, "throw an exception" ).ToLocalChecked() ) );
info.GetIsolate()->ThrowException( exc );
}
void ResolveMessage( v8::Local<v8::Message> message ) {
v8::Isolate* isolate = message->GetIsolate();
v8::Local<v8::Context> context = isolate->GetCurrentContext();
int lineNum = message->GetLineNumber( context ).ToChecked();
v8::String::Utf8Value err_msg( isolate, message->Get() );
v8::String::Utf8Value err_src( isolate, message->GetSourceLine( context ).ToLocalChecked() );
printf( "line %d, [error] %s, [error source] %s", lineNum, *err_msg, *err_src );
}
int main( int argc, char* argv[] ) {
// Initialize V8.
v8::V8::InitializeICUDefaultLocation( argv[0] );
v8::V8::InitializeExternalStartupData( argv[0] );
std::unique_ptr<v8::Platform> platform = v8::platform::NewDefaultPlatform();
v8::V8::InitializePlatform( platform.get() );
v8::V8::Initialize();
// Create a new Isolate and make it the current one.
v8::Isolate::CreateParams create_params;
create_params.array_buffer_allocator =
v8::ArrayBuffer::Allocator::NewDefaultAllocator();
v8::Isolate* isolate = v8::Isolate::New( create_params );
{
v8::Isolate::Scope isolate_scope( isolate );
// Create a stack-allocated handle scope.
v8::HandleScope handle_scope( isolate );
v8::TryCatch trycatch( isolate );
v8::Local<v8::ObjectTemplate> global = v8::ObjectTemplate::New( isolate );
global->Set( isolate, "throwException",
v8::FunctionTemplate::New( isolate, ThrowException ) );
// Create a new context.
v8::Local<v8::Context> context = v8::Context::New( isolate, nullptr, global );
// Enter the context for compiling and running the hello world script.
v8::Context::Scope context_scope( context );
{
// Create a string containing the JavaScript source code.
v8::Local<v8::String> source;
if ( !ReadFile( isolate, fileName ).ToLocal( &source ) ) {
fprintf( stderr, "Error reading '%s'.\n", fileName.c_str() );
return -1;
}
// Compile the source code.
v8::Local<v8::Script> script =
v8::Script::Compile( context, source ).ToLocalChecked();
// Run the script to get the result.
v8::MaybeLocal<v8::Value> result = script->Run( context );
if ( trycatch.HasCaught() ) {
v8::Local<v8::Message> message = trycatch.Message();
ResolveMessage( message );
return -1;
}
}
}
// Dispose the isolate and tear down V8.
isolate->Dispose();
v8::V8::Dispose();
v8::V8::ShutdownPlatform();
delete create_params.array_buffer_allocator;
return 0;
}
file.js
throwException();
运行结果：
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