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message_properties.cpp

Shows how to set and examine message properties.

Shows how to set and examine message properties.

/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
#include <proton/message.hpp>
#include <proton/types.hpp>
#include <iostream>
#include <map>
int main(int argc, char **argv) {
try {
proton::message m;
// Setting properties: legal types are converted automatically to their
// AMQP counterpart.
m.properties().put("short", int16_t(123));
m.properties().put("string", "foo");
m.properties().put("symbol", proton::symbol("sym"));
// Examining properties using proton::get()
// 1 argument get<>() template specifies expected type of property.
std::string s = proton::get<std::string>(m.properties().get("string"));
// 2 argument get, property must have matching type to output argument.
int16_t i;
proton::get(m.properties().get("short"), i);
// Checking property types
proton::type_id type = m.properties().get("symbol").type();
if (type != proton::SYMBOL) {
throw std::logic_error("wrong type!");
}
// proton::scalar has its own ostream <<
std::cout << "using put/get:"
<< " short=" << i
<< " string=" << s
<< " symbol=" << m.properties().get("symbol")
<< std::endl;
// Converting properties to a convertible type
std::cout << "using coerce:"
<< " short(as long)="
<< proton::coerce<long>(m.properties().get("short"))
<< std::endl;
// Extract the properties as a std::map for more complex map operations.
// You can use other map and sequence types to hold a map, see @ref types_page
typedef std::map<std::string, proton::scalar> property_map;
property_map props;
proton::get(m.properties(), props);
for (property_map::iterator i = props.begin(); i != props.end(); ++i) {
std::cout << "props[" << i->first << "]=" << i->second << std::endl;
}
props["string"] = "bar";
props["short"] = 42;
// Update the properties in the message from the modified props map
m.properties() = props;
std::cout << "short=" << m.properties().get("short")
<< " string=" << m.properties().get("string")
<< std::endl;
// proton::get throws an exception if types do not match exactly.
try {
proton::get<uint32_t>(m.properties().get("short")); // bad: uint32_t != int16_t
throw std::logic_error("expected exception");
} catch (const proton::conversion_error& e) {
std::cout << "expected conversion_error: \"" << e.what() << '"' << std::endl;
}
// proton::coerce throws an exception if types are not convertible.
try {
proton::get<uint32_t>(m.properties().get("string")); // bad: string to uint32_t
throw std::logic_error("expected exception");
} catch (const proton::conversion_error& e) {
std::cout << "expected conversion_error: \"" << e.what() << '"' << std::endl;
}
return 0;
} catch (const std::exception& e) {
std::cerr << "unexpected exception: " << e.what() << std::endl;
return 1;
}
}
proton::map
A collection of key-value pairs.
Definition map.hpp:69
proton::map::get
T get(const K &k) const
Get the map entry for key k.
proton::map::put
void put(const K &k, const T &v)
Put a map entry for key k.
proton::message
An AMQP message.
Definition message.hpp:48
proton::message::properties
property_map & properties()
Get the application properties map.
proton::symbol
A string that represents the AMQP symbol type.
Definition symbol.hpp:35
message.hpp
An AMQP message.
proton::get
T get(const scalar &s)
Get a contained value of type T.
Definition scalar.hpp:60
proton::type_id
type_id
An identifier for AMQP types.
Definition type_id.hpp:37
proton::SYMBOL
@ SYMBOL
Variable-length encoded string.
Definition type_id.hpp:58
proton::get< std::string >
std::string get< std::string >(const message_id &x)
Get the std::string value or throw conversion_error.
Definition message_id.hpp:87
proton::conversion_error
An error converting between AMQP and C++ data.
Definition error.hpp:56
types.hpp
Proton types used to represent AMQP types.