简单介绍下mcp是什么

package com.nicksxs.mcp_demo;

import com.jayway.jsonpath.JsonPath;
import org.springframework.ai.tool.annotation.Tool;
import org.springframework.ai.tool.annotation.ToolParam;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestClient;

import java.util.List;
import java.util.Map;

@Service
public class WeatherService {

    private final RestClient restClient;

    public WeatherService() {
        this.restClient = RestClient.builder()
                .baseUrl("https://api.weather.gov")
                .defaultHeader("Accept", "application/geo+json")
                .defaultHeader("User-Agent", "WeatherApiClient/1.0 (your@email.com)")
                .build();
    }

    @Tool(description = "Get weather forecast for a specific latitude/longitude")
    public String getWeatherForecastByLocation(
            double latitude,   // Latitude coordinate
            double longitude   // Longitude coordinate
    ) {
        // 首先获取点位信息
        String pointsResponse = restClient.get()
                .uri("/points/{lat},{lon}", latitude, longitude)
                .retrieve()
                .body(String.class);

        // 从点位响应中提取预报URL
        String forecastUrl = JsonPath.read(pointsResponse, "$.properties.forecast");

        // 获取天气预报
        String forecast = restClient.get()
                .uri(forecastUrl)
                .retrieve()
                .body(String.class);

        // 从预报中提取第一个周期的详细信息
        String detailedForecast = JsonPath.read(forecast, "$.properties.periods[0].detailedForecast");
        String temperature = JsonPath.read(forecast, "$.properties.periods[0].temperature").toString();
        String temperatureUnit = JsonPath.read(forecast, "$.properties.periods[0].temperatureUnit");
        String windSpeed = JsonPath.read(forecast, "$.properties.periods[0].windSpeed");
        String windDirection = JsonPath.read(forecast, "$.properties.periods[0].windDirection");

        // 构建返回信息
        return String.format("Temperature: %s°%s\nWind: %s %s\nForecast: %s",
                temperature, temperatureUnit, windSpeed, windDirection, detailedForecast);
        // Returns detailed forecast including:
        // - Temperature and unit
        // - Wind speed and direction
        // - Detailed forecast description
    }

    @Tool(description = "Get weather alerts for a US state")
    public String getAlerts(@ToolParam(description = "Two-letter US state code (e.g. CA, NY)") String state) {
                
        // 获取指定州的天气警报
        String alertsResponse = restClient.get()
                .uri("/alerts/active/area/{state}", state)
                .retrieve()
                .body(String.class);

        // 检查是否有警报
        List<Map<String, Object>> features = JsonPath.read(alertsResponse, "$.features");
        if (features.isEmpty()) {
            return "当前没有活动警报。";
        }

        // 构建警报信息
        StringBuilder alertInfo = new StringBuilder();
        for (Map<String, Object> feature : features) {
            String event = JsonPath.read(feature, "$.properties.event");
            String area = JsonPath.read(feature, "$.properties.areaDesc");
            String severity = JsonPath.read(feature, "$.properties.severity"); 
            String description = JsonPath.read(feature, "$.properties.description");
            String instruction = JsonPath.read(feature, "$.properties.instruction");

            alertInfo.append("警报类型: ").append(event).append("\n");
            alertInfo.append("影响区域: ").append(area).append("\n");
            alertInfo.append("严重程度: ").append(severity).append("\n");
            alertInfo.append("描述: ").append(description).append("\n");
            if (instruction != null) {
                alertInfo.append("安全指示: ").append(instruction).append("\n");
            }
            alertInfo.append("\n---\n\n");
        }

        return alertInfo.toString();
    }

    // ......
}

public static void main(String[] args) {
        var stdioParams = ServerParameters.builder("java")
                .args("-jar", "/Users/shixuesen/Downloads/mcp-demo/target/mcp-demo-0.0.1-SNAPSHOT.jar")
                .build();

        var stdioTransport = new StdioClientTransport(stdioParams);

        var mcpClient = McpClient.sync(stdioTransport).build();

        mcpClient.initialize();

//        McpSchema.ListToolsResult toolsList = mcpClient.listTools();

        McpSchema.CallToolResult weather = mcpClient.callTool(
                new McpSchema.CallToolRequest("getWeatherForecastByLocation",
                        Map.of("latitude", "47.6062", "longitude", "-122.3321")));
        System.out.println(weather.content());

        McpSchema.CallToolResult alert = mcpClient.callTool(
                new McpSchema.CallToolRequest("getAlerts", Map.of("state", "NY")));

        mcpClient.closeGracefully();
    }