1、JVM调优实战 ​

package cn.itcast.gc.controller;

import cn.itcast.gc.service.MovieService;
import cn.itcast.gc.vo.Movie;
import cn.itcast.gc.vo.MyResult;
import org.apache.commons.lang3.ArrayUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("movie")
public class MovieController {

    @Autowired
    private MovieService movieService;

    @GetMapping("query")
    public MyResult queryMovieList(){
        MyResult myResult = new MyResult();
        List<Movie> movies = this.movieService.queryMovieList();
        myResult.setCount(movies.size());
        myResult.setTop10(movies.subList(0, 9)); //只返回前10条数据,不要将性能损耗在传输上
        return myResult;
    }
}

package cn.itcast.gc.service;

import cn.itcast.gc.vo.Movie;
import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.RandomUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

@Service
public class MovieService {

    private static final List<Movie> MOVIE_LIST = new ArrayList<>();

    @Autowired
    private ResourceLoader resourceLoader;

    @PostConstruct
    public void init() {
        try {
            //读取电影数据文件到内存
            Resource resource = resourceLoader.getResource("classpath:movies.dat");
            InputStream inputStream = resource.getInputStream();
            List<String> lines = IOUtils.readLines(inputStream, "UTF-8");
            for (String line : lines) {
                String[] ss = StringUtils.split(line, "::");
                Movie movie = new Movie();
                movie.setId(Long.valueOf(ss[0]));
                movie.setTitle(ss[1]);
                movie.setPeoples(ss[2]);
                //将数据放入到集合中
                MOVIE_LIST.add(movie);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    public List<Movie> queryMovieList() {
        //随机1w ~ 10w条数据
        int count = RandomUtils.nextInt(10000, 100000);
        List<Movie> list = new ArrayList<>();
        for (int i = 0; i < count; i++) {
            int index = RandomUtils.nextInt(0, MOVIE_LIST.size() - 1);

            Movie movie = MOVIE_LIST.get(index);

            Movie newMovie = new Movie(); //为了加大内存的损耗，创建新的对象
            newMovie.setId(movie.getId());
            newMovie.setPeoples(movie.getPeoples());
            newMovie.setTitle(movie.getTitle());

            list.add(newMovie);
        }
        return list;
    }
}