LIfe is half spent before we know what is it.
缓存List并写入文件持久化
需要缓存一个List集合，比如缓存一个输入框中用户之前输入过的内容，下次当用户再想往输入框中写东西就调用这个缓存的接口，把之前输入过的东西从缓存中取出并返回；
而为了这么一个小小的缓存，引入第三方库Redis或是Cache等也不太划算，于是就可以把缓存写入文件中，序列化到Java虚拟机中，这样就可以支持持久化，即使重启项目缓存的List依然存在；
缓存工具类：
1 package com.xinyan.springcloud.tjt;
2
3
4 import java.io.File;
5 import java.io.FileInputStream;
6 import java.io.FileOutputStream;
7 import java.io.IOException;
8 import java.io.ObjectInputStream;
9 import java.io.ObjectOutputStream;
10 import java.io.Serializable;
11 import java.util.Arrays;
12 import java.util.List;
13
14 public class StreamUtils implements Serializable{
15 private static final long serialVersionUID = 1L;
16 /**
17 * 序列化,List
18 * @param list
19 * @param file
20 * @param <T>
21 * @return
22 */
23 public static <T> boolean writeObject(List<T> list,File file)
24 {
25 T[] array = (T[]) list.toArray();
26 try(ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(file)))
27 {
28 out.writeObject(array);
29 out.flush();
30 return true;
31 }
32 catch (IOException e)
33 {
34 e.printStackTrace();
35 return false;
36 }
37 }
38
39 /**
40 * 反序列化,List
41 * @param file
42 * @param <E>
43 * @return
44 */
45 public static <E> List<E> readObjectForList(File file)
46 {
47 E[] object;
48 try(ObjectInputStream out = new ObjectInputStream(new FileInputStream(file)))
49 {
50 object = (E[]) out.readObject();
51 return Arrays.asList(object);
52 }
53 catch (IOException e)
54 {
55 e.printStackTrace();
56 }
57 catch (ClassNotFoundException e)
58 {
59 e.printStackTrace();
60 }
61 return null;
62 }
63
64 }
测试缓存结果：
1 package com.xinyan.springcloud.tjt;
2
3 import java.io.File;
4 import java.util.ArrayList;
5 import java.util.List;
6
7 import lombok.extern.log4j.Log4j;
8
9 @Log4j
10 public class TestStreamUtils {
11
12 private final static List<String> listSave = new ArrayList<>();
13 private final static String FILE_CACHE = "file-tjt";
14
15 public static void main(String[] args) throws Exception {
16 TestStreamUtils.saveListToJvm("admin");
17 TestStreamUtils.saveListToJvm("user");
18 TestStreamUtils.saveListToJvm("LieIWantTo");
19 Object listFromJvm = TestStreamUtils.getListFromJvm();
20 System.out.println("listFromJvm:"+listFromJvm);
21 }
22
23
24 public static void saveListToJvm(String input) throws Exception{
25 List<String> listInput = new ArrayList<>();
26 listSave.add(input);
27 listInput.addAll(listSave);
28 boolean writeObject = StreamUtils.writeObject(listInput, new File(FILE_CACHE));
29 if (!writeObject) {
30 log.info("saveListToJvm failed!");
31 }
32 }
33
34 public static Object getListFromJvm() {
35 File file = new File(FILE_CACHE);
36 List<Object> readObjectForList = null;
37 if (file.exists()) {
38 readObjectForList = StreamUtils.readObjectForList(file);
39 if (readObjectForList.size() >20) {
40 readObjectForList.remove(0);
41 }
42 }else {
43 log.info("file not exist!");
44 }
45 return readObjectForList;
46 }
47
48 }
测试结果如下图：
