public static String compress ( String str ) { if ( str == null || str . length ( ) == 0 ) { return str ; ByteArrayOutputStream out = new ByteArrayOutputStream ( ) ; GZIPOutputStream gzip = null ; try { gzip = new GZIPOutputStream ( out ) ; gzip . write ( str . getBytes ( ) ) ; } catch ( IOException e ) { e . printStackTrace ( ) ; } finally { if ( gzip != null ) { try { gzip . close ( ) ; } catch ( IOException e ) { e . printStackTrace ( ) ; return new sun . misc . BASE64Encoder ( ) . encode ( out . toByteArray ( ) ) ; * 使用gzip解压缩 * @param compressedStr 压缩字符串 * @return public static String uncompress ( String compressedStr ) { if ( compressedStr == null ) { return null ; ByteArrayOutputStream out = new ByteArrayOutputStream ( ) ; ByteArrayInputStream in = null ; GZIPInputStream ginzip = null ; byte [ ] compressed = null ; String decompressed = null ; try { compressed = new sun . misc . BASE64Decoder ( ) . decodeBuffer ( compressedStr ) ; in = new ByteArrayInputStream ( compressed ) ; ginzip = new GZIPInputStream ( in ) ; byte [ ] buffer = new byte [ 1024 ] ; int offset = - 1 ; while ( ( offset = ginzip . read ( buffer ) ) != - 1 ) { out . write ( buffer , 0 , offset ) ; decompressed = out . toString ( ) ; } catch ( IOException e ) { e . printStackTrace ( ) ; } finally { if ( ginzip != null ) { try { ginzip . close ( ) ; } catch ( IOException e ) { if ( in != null ) { try { in . close ( ) ; } catch ( IOException e ) { if ( out != null ) { try { out . close ( ) ; } catch ( IOException e ) { return decompressed ;

方法二：用org.apache.commons.codec.binary.Base64

* 使用org.apache.commons.codec.binary.Base64压缩字符串 * @param str 要压缩的字符串 * @return public static String compress ( String str ) { if ( str == null || str . length ( ) == 0 ) { return str ; return Base64 . encodeBase64String ( str . getBytes ( ) ) ; * 使用org.apache.commons.codec.binary.Base64解压缩 * @param compressedStr 压缩字符串 * @return public static String uncompress ( String compressedStr ) { if ( compressedStr == null ) { return null ; return Base64 . decodeBase64 ( compressedStr ) ;

在web项目中，服务器端将加密后的字符串返回给前端，前端再通过ajax请求将加密字符串发送给服务器端处理的时候，在http传输过程中会改变加密字符串的内容，导致服务器解压压缩字符串发生异常：

java.util.zip.ZipException: Not in GZIP format
解决方法：
 
在字符串压缩之后,将压缩后的字符串BASE64加密,在使用的时候先BASE64解密再解压即可
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.GZIPInputStream;
import java....
import java.io.*;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
 * GZIP工具类
 * @author [email protected]
 * @date 2019/7/19 下午7:03
public...
// 使用GZIP算法压缩字符串
ByteArrayOutputStream baos = new ByteArrayOutputStream();
GZIPOutputStream gzip = new GZIPOutputStream(baos);
gzip.write(str.getBytes("UTF-8"));
gzip.close();
byte[] compressedData = baos.toByteArray();
// 将压缩后的字节流保存到数据库中
// 假设使用JDBC连接MySQL数据库
String url = "jdbc:mysql://localhost:3306/mydb";
String username = "root";
String password = "password";
Connection conn = DriverManager.getConnection(url, username, password);
PreparedStatement stmt = conn.prepareStatement("INSERT INTO mytable (compressed_data) VALUES (?)");
stmt.setBytes(1, compressedData);
stmt.executeUpdate();
stmt.close();
conn.close();
注意，当从数据库中读取压缩后的数据时，需要使用GZIP解压缩算法将压缩后的字节流解压缩为原始字符串。以下是一个简单的示例代码：
```java
// 从数据库中读取压缩后的数据
// 假设使用JDBC连接MySQL数据库
String url = "jdbc:mysql://localhost:3306/mydb";
String username = "root";
String password = "password";
Connection conn = DriverManager.getConnection(url, username, password);
PreparedStatement stmt = conn.prepareStatement("SELECT compressed_data FROM mytable WHERE id=?");
stmt.setInt(1, 1);
ResultSet rs = stmt.executeQuery();
rs.next();
byte[] compressedData = rs.getBytes(1);
rs.close();
stmt.close();
conn.close();
// 使用GZIP算法解压缩数据
ByteArrayInputStream bais = new ByteArrayInputStream(compressedData);
GZIPInputStream gzip = new GZIPInputStream(bais);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len;
while ((len = gzip.read(buffer)) > 0) {
    baos.write(buffer, 0, len);
gzip.close();
baos.close();
String str = new String(baos.toByteArray(), "UTF-8");
System.out.println(str); // 输出 "Hello, world!"