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|
### jsoncons::jsonschema::json_schema<Json>::is_valid
```cpp
bool is_valid(const Json& instance) const;
```
Validates input JSON against a JSON Schema and returns false upon the
first schema violation.
#### Parameters
<table>
<tr>
<td>instance</td>
<td>Input Json</td>
</tr>
</table>
#### Return value
`true` if the instance is valid, otherwise `false`.
#### Exceptions
None.
### Examples
#### Validate before decode
```cpp
#include <jsoncons/json.hpp>
#include <jsoncons_ext/jsonschema/jsonschema.hpp>
#include <iostream>
#include <cassert>
#include <variant>
using jsoncons::json;
namespace jsonschema = jsoncons::jsonschema;
namespace ns {
struct os_properties {
std::string command;
};
struct db_properties {
std::string query;
};
struct api_properties {
std::string target;
};
struct job_properties {
std::string name;
std::variant<os_properties, db_properties, api_properties> run;
};
} // namespace ns
JSONCONS_N_MEMBER_TRAITS(ns::os_properties, 1, command)
JSONCONS_N_MEMBER_TRAITS(ns::db_properties, 1, query)
JSONCONS_N_MEMBER_TRAITS(ns::api_properties, 1, target)
JSONCONS_N_MEMBER_TRAITS(ns::job_properties, 2, name, run)
int main()
{
std::string schema_str = R"(
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"title": "job",
"description": "job properties json schema",
"$defs": {
"os_properties": {
"type": "object",
"properties": {
"command": {
"description": "this is the OS command to run",
"type": "string",
"minLength": 1
}
},
"required": [ "command" ],
"additionalProperties": false
},
"db_properties": {
"type": "object",
"properties": {
"query": {
"description": "this is db query to run",
"type": "string",
"minLength": 1
}
},
"required": [ "query" ],
"additionalProperties": false
},
"api_properties": {
"type": "object",
"properties": {
"target": {
"description": "this is api target to run",
"type": "string",
"minLength": 1
}
},
"required": [ "target" ],
"additionalProperties": false
}
},
"type": "object",
"properties": {
"name": {
"description": "name of the flow",
"type": "string",
"minLength": 1
},
"run": {
"description": "job run properties",
"type": "object",
"oneOf": [
{ "$ref": "#/$defs/os_properties" },
{ "$ref": "#/$defs/db_properties" },
{ "$ref": "#/$defs/api_properties" }
]
}
},
"required": [ "name", "run" ],
"additionalProperties": false
}
)";
std::string data_str = R"(
{
"name": "testing flow",
"run" : {
"command": "some command"
}
}
)";
try
{
json schema = json::parse(schema_str);
// Throws schema_error if JSON Schema compilation fails
jsonschema::json_schema<json> compiled = jsonschema::make_json_schema(std::move(schema));
// Test that input is valid before attempting to decode
json data = json::parse(data_str);
if (compiled.is_valid(data))
{
const ns::job_properties v = data.as<ns::job_properties>();
std::string output;
jsoncons::encode_json_pretty(v, output);
std::cout << output << '\n';
// Verify that output is valid
json test = json::parse(output);
assert(compiled.is_valid(test));
}
else
{
std::cout << "Invalid input\n";
}
}
catch (const std::exception& e)
{
std::cout << e.what() << '\n';
}
}
```
Output:
```
{
"name": "testing flow",
"run": {
"command": "some command"
}
}
```
|
