180918-JDK之Deflater壓縮與Inflater解壓

時間  2019-12-07
標籤 jdk deflater 壓縮 inflater 解壓 欄目 Java 简体版
原文   原文鏈接

JDK 壓縮與解壓工具類

在實際的應用場景中，特別是對外傳輸數據時，將原始數據壓縮以後丟出去，能夠說是很是常見的一個case了，日常卻是沒有直接使用JDK原生的壓縮工具類，使用Protosutff和Kryo的機會較多,正好在實際的工做場景中遇到了，如今簡單的看下使用姿式html

I. 壓縮與解壓工具類

1. 基本實現

主要藉助的就是Deflater, Inflater兩個工具類，其使用姿式以下java

public static String uncompress(byte[] input) throws IOException {
    Inflater inflater = new Inflater();
    inflater.setInput(input);
    ByteArrayOutputStream baos = new ByteArrayOutputStream(input.length);
    try {
        byte[] buff = new byte[1024];
        while (!inflater.finished()) {
            int count = inflater.inflate(buff);
            baos.write(buff, 0, count);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        baos.close();
    }
    inflater.end();
    byte[] output = baos.toByteArray();
    return new String(output, "UTF-8");
}

public static byte[] compress(byte[] data) throws IOException {
    byte[] output;
    Deflater compress = new Deflater();

    compress.reset();
    compress.setInput(data);
    compress.finish();
    ByteArrayOutputStream bos = new ByteArrayOutputStream(data.length);
    try {
        byte[] buf = new byte[1024];
        while (!compress.finished()) {
            int i = compress.deflate(buf);
            bos.write(buf, 0, i);
        }
        output = bos.toByteArray();
    } catch (Exception e) {
        output = data;
        e.printStackTrace();
    } finally {
        bos.close();
    }
    compress.end();
    return output;
}

一個簡單的測試git

public static void main(String[] args) throws IOException {
    StringBuilder builder = new StringBuilder();
    for (int i = 0; i < 200; i++) {
        builder.append('a' + (new Random().nextInt() * 26));
    }
    String text = builder.toString();
    byte[] compres = compress(text.getBytes());
    System.out.println(compres.length + " : " + text.getBytes().length);

    String res = uncompress(compres);
    System.out.println("uncompress! \n" + text + "\n" + res);
}

輸出結果github

1011 : 1974
uncompress! 
1159641073884270587-148914555-876348695-140903655914152858511750740619-504526839109631208315104321891746743931-228808979-1303586499-19431155411964999751-1784318475-954798177-1812907183-831342707-3149322476028964551802022597-269963287-6384200011467670385844411707877038035412670417-1119826115558346219-959513147646693111435818855-32626587-18184494797054550038966016212145089137523302939171183465807867207-5294746515903446057333959811216956465-11772186456902770294071039871896527261-126190055310658640239029635411410052621945318513-1099749933-2044334159884087065-1705740759-1313321287-1408007761-12659778231544522691472523171153203782987609706919936632357801287155512488271333115291-1121944135941979389-179880545175884207196204559-2097788799145839653133892163716038492252042396151523357607329397509-2453452914618397691174247129-542507633-1893723573237001573-84175562119492726191070559557-875056377-1763237523-662399435-170798495-12405874171550890051-1938474621-701626601-1246867757-1138873077164155271023310391435811251050668025181338411-7641844471088518205-1570482881-1690731767-954924683-213656821149494003-544272515-9322840891981997411254437701-183054198720365002211448655569-54030518916444117051191350451-900732825-2072105047160877226512403288354302424851213478975-57604286986096457192173124564975571096304687-213425653510984804314132356831371957625714091709-327695077-182546427-372769058150182636433743131293942149315625331-1010625457741185365-81246881-565236593-1937214707-2090999425-1673181289-1110250756450022071917863643-127217577910228760391902441297-31318475-535669437-1151216791170962161121375401911260706331-1873591233-495048743-8876731551362670289-686442615-6752584831233249861-3467630691547253127-345092207-908370541-1788351797644350365-67770933-4703179231930520693138257968522450375-1171662023-5791753311816936409-1745781765-922801857281665531707439257928142703-367587763829971705455779401438501763-1398546079-606883161-924403277-1617582925-2005411841279115903
1159641073884270587-148914555-876348695-140903655914152858511750740619-504526839109631208315104321891746743931-228808979-1303586499-19431155411964999751-1784318475-954798177-1812907183-831342707-3149322476028964551802022597-269963287-6384200011467670385844411707877038035412670417-1119826115558346219-959513147646693111435818855-32626587-18184494797054550038966016212145089137523302939171183465807867207-5294746515903446057333959811216956465-11772186456902770294071039871896527261-126190055310658640239029635411410052621945318513-1099749933-2044334159884087065-1705740759-1313321287-1408007761-12659778231544522691472523171153203782987609706919936632357801287155512488271333115291-1121944135941979389-179880545175884207196204559-2097788799145839653133892163716038492252042396151523357607329397509-2453452914618397691174247129-542507633-1893723573237001573-84175562119492726191070559557-875056377-1763237523-662399435-170798495-12405874171550890051-1938474621-701626601-1246867757-1138873077164155271023310391435811251050668025181338411-7641844471088518205-1570482881-1690731767-954924683-213656821149494003-544272515-9322840891981997411254437701-183054198720365002211448655569-54030518916444117051191350451-900732825-2072105047160877226512403288354302424851213478975-57604286986096457192173124564975571096304687-213425653510984804314132356831371957625714091709-327695077-182546427-372769058150182636433743131293942149315625331-1010625457741185365-81246881-565236593-1937214707-2090999425-1673181289-1110250756450022071917863643-127217577910228760391902441297-31318475-535669437-1151216791170962161121375401911260706331-1873591233-495048743-8876731551362670289-686442615-6752584831233249861-3467630691547253127-345092207-908370541-1788351797644350365-67770933-4703179231930520693138257968522450375-1171662023-5791753311816936409-1745781765-922801857281665531707439257928142703-367587763829971705455779401438501763-1398546079-606883161-924403277-1617582925-2005411841279115903

2. 注意事項

上面這個運做的還挺好，但在接入使用時，老是提示java.util.zip.DataFormatException: incorrect header check, 由於接受的是第三方傳遞過來的壓縮數據，比較坑爹的是對方就寫了個Deflater壓縮，而後什麼都沒有了，那麼這個是啥緣由呢？app

其實看下Deflater的構造方法，發現還能夠傳一個boolean值(nowrap), 官方說明是框架

/**
 * Creates a new compressor using the specified compression level.
 * If 'nowrap' is true then the ZLIB header and checksum fields will
 * not be used in order to support the compression format used in
 * both GZIP and PKZIP.
 * @param level the compression level (0-9)
 * @param nowrap if true then use GZIP compatible compression
 */
public Deflater(int level, boolean nowrap) {
    this.level = level;
    this.strategy = DEFAULT_STRATEGY;
    this.zsRef = new ZStreamRef(init(level, DEFAULT_STRATEGY, nowrap));
}

簡單來講，就是壓縮時，若是nowrap爲true，那麼解壓時也要爲true；不然對不上時，就會拋異常dom

接下來簡單對比下兩種不一樣傳參的狀況，首先更新下工具類函數

public static String uncompress(byte[] input, boolean nowrap) throws IOException {
    Inflater inflater = new Inflater(nowrap);
    inflater.setInput(input);
    ByteArrayOutputStream baos = new ByteArrayOutputStream(input.length);
    try {
        byte[] buff = new byte[1024];
        while (!inflater.finished()) {
            int count = inflater.inflate(buff);
            baos.write(buff, 0, count);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        baos.close();
    }
    inflater.end();
    byte[] output = baos.toByteArray();
    return new String(output);
}

public static byte[] compress(byte[] data, boolean nowrap) throws IOException {
    byte[] output;
    Deflater compress = new Deflater(Deflater.DEFAULT_COMPRESSION, nowrap);

    compress.reset();
    compress.setInput(data);
    compress.finish();
    ByteArrayOutputStream bos = new ByteArrayOutputStream(data.length);
    try {
        byte[] buf = new byte[1024];
        while (!compress.finished()) {
            int i = compress.deflate(buf);
            bos.write(buf, 0, i);
        }
        output = bos.toByteArray();
    } catch (Exception e) {
        output = data;
        e.printStackTrace();
    } finally {
        bos.close();
    }
    compress.end();
    return output;
}

測試以下工具

public static void main(String[] args) throws IOException {
    StringBuilder builder = new StringBuilder();
    for (int i = 0; i < 1000; i++) {
        builder.append('a' + (new Random().nextInt() * 26));
    }
    String text = builder.toString();
    byte[] compres = compress(text.getBytes(), true);
    System.out.println(compres.length + " : " + text.getBytes().length);
    String res = uncompress(compres, true);
    System.out.println(res.equals(text));


    byte[] compres2 = compress(text.getBytes(), false);
    System.out.println(compres2.length + " : " + text.getBytes().length);
    String res2 = uncompress(compres2, false);
    System.out.println(res2.equals(text));
}

輸出結果以下，從大小來看，前者小那麼一點點性能

5086 : 9985
true
5092 : 9985
true

3. 小結

通常來講，jdk自帶的壓縮與解壓，除了方便以外，可能優點並非那麼的大，這裏盜一張網上的對比表格

如下來自: [java]序列化框架性能對比（kryo、hessian、java、protostuff）

優勢 缺點
kryo 速度快，序列化後體積小 跨語言支持較複雜
hessian 默認支持跨語言 較慢
protostuff 速度快，基於protobuf 需靜態編譯
Protostuff-Runtime 無需靜態編譯，但序列化前需預先傳入schema 不支持無默認構造函數的類，反序列化時需用戶本身初始化序列化後的對象，其只負責將該對象進行賦值
jdk 使用方便，可序列化全部類 速度慢，佔空間

其次，在使用java的壓縮與解壓時，須要注意下，nowrap這個參數，須要保持一致，不然會報錯

II. 其餘

1. 一灰灰Blog： https://liuyueyi.github.io/hexblog

一灰灰的我的博客，記錄全部學習和工做中的博文，歡迎你們前去逛逛

2. 聲明

盡信書則不如，已上內容，純屬一家之言，因我的能力有限，不免有疏漏和錯誤之處，如發現bug或者有更好的建議，歡迎批評指正，不吝感激

3. 掃描關注

一灰灰blog

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