Writing XML Document to InputStream using dom4j

Posted on 2020-11-06 by robin

When tring to upload a XML file to AWS S3, I found that it’s not allowed to create a tmp file in server local, so I had to transfer the file as InputStream at first and upload it later.

This is the code of transfering the XML Document instance to InputStream and Byte array:

public static InputStream documentToInputStream(Document doc) throws IOException {
    byte[] bytes = documentToBytes(doc);
    return new ByteArrayInputStream(bytes);
}


public static byte[] documentToBytes(Document doc) throws IOException {
    try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
        XMLWriter xmlWriter = new XMLWriter(outputStream, OutputFormat.createCompactFormat());
        xmlWriter.write(doc);
        xmlWriter.close();
        return outputStream.toByteArray();
    }
}

public static InputStream documentToInputStream(Document doc) throws IOException {

byte[] bytes = documentToBytes(doc);

return new ByteArrayInputStream(bytes);

}

public static byte[] documentToBytes(Document doc) throws IOException {

try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {

XMLWriter xmlWriter = new XMLWriter(outputStream, OutputFormat.createCompactFormat());

xmlWriter.write(doc);

xmlWriter.close();

return outputStream.toByteArray();

}

As dom4j is been used to generate the XML, some classes from which (e.g. Document, XMLWriter) can be found in the code.

Uploading files to AWS S3 By Java SpringBoot

Posted on 2020-11-03 by robin

This is a demo of uploading files to AWS S3 using Java SpringBoot.

First, we need to add the dependency of AWS S3:

<dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-java-sdk-s3</artifactId>
    <version>1.11.891</version>
</dependency>

<groupId>com.amazonaws</groupId>

</dependency>

Then add these configs in application.yml:

custom:
  aws:
    access-key: CHOBITACCESSKEY
    secret-key: CHOBIT/THISIS006SECRET007Key/dotORG
    bucket: zhyea
    endpoint: www.zhyea.com:80

custom:

aws:

access-key: CHOBITACCESSKEY

secret-key: CHOBIT/THISIS006SECRET007Key/dotORG

bucket: zhyea

endpoint: www.zhyea.com:80

The accessKey, secretKey and bucket is nesscessary which can be found in aws’ admin dashboard. Continue reading →

Reading files from SpringBoot resources folder

Posted on 2020-10-30 by robin

Reading files from a SpringBoot jar is something a little complex.

I had tried to read a file from springboot resources folder using java.io.File. This is the code:

public static void readFromResources() {
    String path = "config.xml";
    String fullPath = IoKit.class.getClassLoader().getResource(path).getFile();
    File file = new File(fullPath);
    System.out.println(file.exists());
}

public static void readFromResources() {

String path = "config.xml";

String fullPath = IoKit.class.getClassLoader().getResource(path).getFile();

File file = new File(fullPath);

System.out.println(file.exists());

}

And I got the FileNotFoundException :

java.io.FileNotFoundException: class path resource [config.xml] cannot be resolved to absolute file path because it does not reside in the file system: file:/data/www/htdocs/my-app/lib/my-app.jar!/BOOT-INF/class
es!/config.xml
        at org.springframework.util.ResourceUtils.getFile(ResourceUtils.java:217)
        at org.springframework.core.io.AbstractFileResolvingResource.getFile(AbstractFileResolvingResource.java:154)
        at org.chobit.IoKit.readResources(IoKit.java:46)
        at org.chobit.IoKitTest.readResources(IoKitTest.java:67)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:893)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:798)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)

java.io.FileNotFoundException: class path resource [config.xml] cannot be resolved to absolute file path because it does not reside in the file system: file:/data/www/htdocs/my-app/lib/my-app.jar!/BOOT-INF/class

es!/config.xml

at org.springframework.util.ResourceUtils.getFile(ResourceUtils.java:217)

at org.springframework.core.io.AbstractFileResolvingResource.getFile(AbstractFileResolvingResource.java:154)

at org.chobit.IoKit.readResources(IoKit.java:46)

at org.chobit.IoKitTest.readResources(IoKitTest.java:67)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:498)

at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)

at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)

at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:893)

at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:798)

at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)

at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)

Since there is no path like file:/data/www/htdocs/my-app/lib/my-app.jar!/BOOT-INF/class existed in my computer, I got the exception. Continue reading →

Package all files in Java resources’ subdirectories

Posted on 2020-10-27 by robin

Maybe mvn clean package is one of the easiest operation in java programing. Howerver, I recently encountered a problem of packaging, which took up some of my time.

This was the initial package config in maven pom:

<resources>
    <resource>
        <directory>src/main/resources</directory>
        <filtering>true</filtering>
    </resource>
</resources>

<directory>src/main/resources</directory>

</resource>

</resources>

And this is the path of the file I wanted to package and read:

src/main/resources/template/xxx.xml

1	src/main/resources/template/xxx.xml

Executing the package command (mvn clean package) and opening the jar with compression software (e.g. WinRAR), the file was expected to locate at BOOT-INFO/class/template. However I could not find it. Though all files in resources folder directly existed, the others in subdirectories was not there. Continue reading →

How to make Jackson to avoid Escaping Backslash

Posted on 2020-10-24 by robin

As I tried to deserialize a json string from database with jackson, I received error message like this:

Exception in thread "main" com.fasterxml.jackson.core.JsonParseException: Unrecognized character escape 'W' (code 87)
 at [Source: (String)"{"text":"Hello \World!"}"; line: 1, column: 18]
	at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1840)
	at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:712)
	at com.fasterxml.jackson.core.base.ParserBase._handleUnrecognizedCharacterEscape(ParserBase.java:1031)
	at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._decodeEscaped(ReaderBasedJsonParser.java:2545)
	at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._finishString2(ReaderBasedJsonParser.java:2066)
	at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._finishString(ReaderBasedJsonParser.java:2039)
	at com.fasterxml.jackson.core.json.ReaderBasedJsonParser.getText(ReaderBasedJsonParser.java:294)
	at com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer$Vanilla.deserialize(UntypedObjectDeserializer.java:672)
	at com.fasterxml.jackson.databind.deser.std.MapDeserializer._readAndBindStringKeyMap(MapDeserializer.java:527)
	at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:364)
	at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:29)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4202)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3205)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3173)
	at org.chobit.calf.MyApp.main(MyApp.java:23)

Exception in thread "main" com.fasterxml.jackson.core.JsonParseException: Unrecognized character escape 'W' (code 87)

at [Source: (String)"{"text":"Hello \World!"}"; line: 1, column: 18]

at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1840)

at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:712)

at com.fasterxml.jackson.core.base.ParserBase._handleUnrecognizedCharacterEscape(ParserBase.java:1031)

at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._decodeEscaped(ReaderBasedJsonParser.java:2545)

at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._finishString2(ReaderBasedJsonParser.java:2066)

at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._finishString(ReaderBasedJsonParser.java:2039)

at com.fasterxml.jackson.core.json.ReaderBasedJsonParser.getText(ReaderBasedJsonParser.java:294)

at com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer$Vanilla.deserialize(UntypedObjectDeserializer.java:672)

at com.fasterxml.jackson.databind.deser.std.MapDeserializer._readAndBindStringKeyMap(MapDeserializer.java:527)

at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:364)

at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:29)

at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4202)

at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3205)

at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3173)

at org.chobit.calf.MyApp.main(MyApp.java:23)

The json string is:

{"text":"Hello \World!"}

1	{"text":"Hello \World!"}

It’s the Backslash in the source json string which lead to the error. Continue reading →

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Category Archives: Java

Writing XML Document to InputStream using dom4j

Uploading files to AWS S3 By Java SpringBoot

Reading files from SpringBoot resources folder

Package all files in Java resources’ subdirectories

How to make Jackson to avoid Escaping Backslash