[internship] solve the problem of too long request parameters

And to solve bug La ！！！

Due to the front-end transmission json Too long data leads to too long request parameters , Finally, a null pointer exception appears .
HTTP/1.1 414 Request-URI Too Large

resolvent ：
Reference resources ：Java Use GZIP Compress and decompress （GZIPOutputStream,GZIPInputStream）
Use gzip Compress / Decompress the string

One 、 Use gzip Compress string (str The string to compress )

①

Reference resources ：
Java ByteArrayOutputStream class

// Create a 32 byte （ Default size ） The buffer 
ByteArrayOutputStream out = new ByteArrayOutputStream();

Source code ：

②

// Create with default buffer size out New byte array output stream object .
GZIPOutputStream gzip = new GZIPOutputStream(out);

Reference resources ：
Java_io System of FilterInputStream/FilterOutputStream brief introduction 、 Go into the source code and examples ——07

Source code ：
Create a new output stream with the default buffer size .
The new output stream instance is through the call 2 Parameter constructor GZIPOutputStream（out,false） Created .

Create a new output stream using the default buffer size and the specified refresh mode .
Parameters ：
out– Output stream syncFlush– If the inheritance of this instance flush（） The method call is true, Then use flush mode Deflater Refresh compressor . Before refreshing the output stream SYNC\u Refresh , Otherwise, only refresh the output stream .

③

gzip.write(str.getBytes());

getBytes() yes Java The programming language converts a string into a byte array byte[] Methods .

	//getBytes()  Source code ：
	public byte[] getBytes() {
    
        return StringCoding.encode(value, off:0, value.length);
    }

write Source code ：
take b.length Bytes written to this output stream .
FilterOutputStream Of write Method uses parameters b、0 and b.length Call its three parameters write Method .
Be careful , This method does not use a single parameter b Call the single parameter of its bottom layer flow write Method .

Of its three parameters write Method source code ：
From the offset off Start , Will specify... In the byte array len Bytes written to this output stream .
FilterOutputStream Of write Method calls the... Of the last parameter on each byte write Method to output .
Please note that , This method will not call its underlying input stream with the same parameters write Method .FilterOutputStream Subclasses of should provide a more efficient implementation of this method .

Writes the specified bytes to this output stream .
FilterOutputStream Of write Method calls its underlying output stream write Method , The perform . write in （b）. Realization OutputStream Abstract writing method of .

Writes the specified bytes to this output stream .
The general convention of writing is to write a byte to the output stream . The bytes to be written are parameters b Eight low positions . Ignore b Of 24 A high position .OutputStream Subclasses of must provide implementations of this method .

④

if (gzip != null) {
    
	try {
    
		gzip.close();
	} catch (IOException e) {
    
		e.printStackTrace();
	}
}

close Source code ：
Write the remaining compressed data to the output stream and close the underlying stream .

private boolean closed = false;
boolean usesDefaultDeflater = false;

Write compressed data to the output stream without closing the underlying stream .
When multiple filters are applied continuously to the same output stream , Please use this method .

Turn off the compressor and discard any unprocessed input . When the compressor is no longer in use , This method should be called , But it will also be finalize（） Method auto call . After calling this method ,Deflater The behavior of the object is undefined .

Close this output stream and release any system resources associated with it .
The general convention for closing is to close the output stream . Closed stream cannot perform output operation , Can't reopen .
OutputStream Of close Method doesn't work .

⑤

// code - Compress 
return new sun.misc.BASE64Encoder().encode(out.toByteArray());

Reference resources ：

• sun.misc.BASE64Encoder Detailed explanation
• base64 Encoding, decoding and sun.misc.BASE64Decoder Usage of
• About Base64 code (Encode) And decoding (Decode) In several ways , There are many roads in here

stay JAVA In order to achieve Base64 It is very easy to encode and decode , because JDK There are already ready-made classes in ：

// code ：
String src ="BASE64 Coding test ";  
sun.misc.BASE64Encoder en = new sun.misc.BASE64Encoder(); 
String encodeStr = en.encode(src.getBytes());     

// decode ：
sun.misc.BASE64Decoder dec = newsun.misc.BASE64Decoder(); 
byte[] data = dec.decodeBuffer(decodeStr); 

Two 、 Use gzip decompression (compressedStr Compress string )

①

// initialization , Create a buffer partition of default size 
ByteArrayOutputStream out = new ByteArrayOutputStream();
ByteArrayInputStream in = null;
GZIPInputStream ginzip = null;
byte[] compressed = null;
String decompressed = null;

②

//decodeBuffer() decode 
compressed = new sun.misc.BASE64Decoder().decodeBuffer(compressedStr);

③

 in = new ByteArrayInputStream(compressed);

establish ByteArrayInputStream, For use buf As an array of buffers . Buffer array not copied .pos The initial value of 0,count The initial value of buf The length of .

④

ginzip = new GZIPInputStream(in);

Create a new input stream with the default buffer size .

⑤

while ((offset = ginzip.read(buffer)) != -1) {
    
	out.write(buffer, 0, offset);
}

Read bytes at most . Set the data length bytes in this input stream as a byte array . This method will block , Until some input is available .
This method only performs call reading （b,0,b.length） And return the result . It is important to , It doesn't apply to . Change it to （b）;FilterInputStream Some subclasses of depend on the implementation strategy actually used .

Read up to... From this input stream len Bytes of data into a byte array . If len Not zero , This method will block , Until some input is available ; otherwise , Do not read any bytes , And back to 0.
This method is only executed in . Read （b,off,len） And return the result .
Parameters ：
b– Buffer for reading data .off– Target array b len Start offset in – The maximum number of bytes read .

From the offset off Start , Will specify... In the byte array len Bytes are written to this byte array output stream .

⑥

// Convert to String type 
decompressed = out.toString();

in the light of java, Be careful ：

• If the JDK Version less than 1.8, Please use org.apache.commons.codec.binary.Base64;
• If the JDK The version is greater than 1.8, Please use java.util.Base64;
• Use org.apache.commons.codec.binary.Base64 when , To select and project JDK coincidental JAR package , Otherwise, the effect will not be achieved ;
• java.util.Base64 And org.apache.commons.codec.binary.Base64 Packet collision , Cannot exist in a class at the same time ;
• Be careful ,UTF-8 and GBK Chinese format Base64 The coding results are different .

3、 ... and 、 modify service Implementation class -Json Convert to sql In the method conditionJson Compression format for

original ：

params.put("conditionJson", URLEncoder.encode(tagInfo.getGenerationLogic(),"UTF-8")); // conditionJson Conditions json Field   Same as   Generate logical fields ：generationLogic

After modification ： request url The compressed parameters will not be too long

// Compressed logic json
String compressGenerationLogic = CompressUtil.compress(tagInfo.getGenerationLogic());
params.put("conditionJson", URLEncoder.encode(Base64.encodeBase64String(compressGenerationLogic.getBytes()),"UTF-8")); 

URLEncoder.encode(String s, String enc):
s– String to translate .enc– The name of the supported character encoding .

URLEncoder.encode(tagInfo.getGenerationLogic(),"UTF-8")

Use a specific encoding scheme to convert the string to application/x-www-form-urlencoded Format . This method uses the provided encoding scheme to obtain the bytes of unsafe characters .

String encode(String s, String enc)

Use base64 Algorithm encodes binary data , But do not block the output .
notes ： We block the behavior of this method from multiple lines （commons-codec-1.4） Change to single line non blocking （commons-codec-1.5）.

Use base64 Algorithm encodes binary data , You can choose to block the output into 76 A block of characters .
isChunked– If true, Then this encoder will base64 Output is divided into 76 A block of characters

Use base64 Algorithm encodes binary data , You can choose to block the output into 76 A block of characters .
Parameters ：
binaryData– An array containing binary data to be encoded .
isChunked– If true, Then this encoder will base64 Output is divided into 76 A block of characters
urlSafe– If true, Then this encoder will send - and _ Not the usual + and / character . Be careful ： Use URL Do not add padding when encoding the safety alphabet .

Use base64 Algorithm encodes binary data , You can choose to block the output into 76 A block of characters .
Parameters ：
binaryData– An array containing binary data to be encoded .
isChunked– If true, Then this encoder will base64 Output is divided into 76 A block of characters
urlSafe– If true, Then this encoder will send - and _ Not the usual + and / character .
Be careful ： Use URL Do not add padding when encoding the safety alphabet .
maxResultSize– The maximum result size to accept .

Four 、 modify Controller The interface of

Go to request Add conditions to json— It is decompressed .

String decodeConditionJson = new String(Base64.decodeBase64(request.getConditionJson()));
request.setConditionJson(CompressUtil.uncompress(decodeConditionJson));

take Base64 The string is decoded into octets ：

Decode contains N String of characters in hexadecimal letters .

Decode contains N Byte array of characters in hexadecimal letters .

The processing flow of the sender before data transmission is as follows （ The receiving ends are mutually inverse ）：
1. First sign the original string , To ensure that the signature is faithful to the original content ;
2. Then compress , In order to simplify the size of the content , Improve the efficiency of subsequent encryption and transmission ;
3. Finally, encrypt , Ensure data security .