I am new to protocol buffers so I was trying out an example code. My proto file code is below:
syntax="proto2";
package test;
option java_package="com.example.test";
message Test1 {
required int32 a = 1;
}
I compiled it using protec correctly. After that I wanted to use it out in a Java code. The code is
import com.example.test.Test1OuterClass;
import com.example.test.Test1OuterClass.Test1;
import java.io.*;
import java.util.*;
public class Testing {
public static void main(String[] args) throws Exception{
Scanner sc = new Scanner(System.in);
System.out.println("Enter a number:");
int a = sc.nextInt();
Test1.Builder t = Test1.newBuilder();
t.setA(a).build();
}
}
Now I want to implement encoding in this but I am not able to do it. I searched online and read the Google documentation but couldn't understand how to do it. Can someone tell me how to perform basic encoding here?
Useful links related to encoding in protobufs are appreciated too.
Test1 obj = t.setA(a).build();
then
byte[] arr = obj.toByteArray();
or
obj.writeTo(outputStream);
Related
This question already has answers here:
Java interpreter? [closed]
(10 answers)
Closed 9 years ago.
For debug reasons, I want to be able to run code that is typed in through the console. For example:
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
while(true){
String str = br.readLine(); //This can return 'a = 5;','b = "Text";' or 'pckg.example.MyClass.run(5);'
if(str == null)
return;
runCode(str); //How would I do this?
}
PLEASE DON'T ACTUALLY USE THIS
I was under the assumption you wanted to evaluate a string as Java code, not some scripting engine like Javascript, so
I created this on a whim after reading this, using the compiler API mark mentioned. It's probably very bad practice but it (somewhat) works like you wanted it to. I doubt it'll be much use in debugging since it runs the code in the context of a new class. Sample usage is included at the bottom.
import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
public class main {
public static void runCode(String s) throws Exception{
JavaCompiler jc = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager sjfm = jc.getStandardFileManager(null, null, null);
File jf = new File("test.java"); //create file in current working directory
PrintWriter pw = new PrintWriter(jf);
pw.println("public class test {public static void main(){"+s+"}}");
pw.close();
Iterable fO = sjfm.getJavaFileObjects(jf);
if(!jc.getTask(null,sjfm,null,null,null,fO).call()) { //compile the code
throw new Exception("compilation failed");
}
URL[] urls = new URL[]{new File("").toURI().toURL()}; //use current working directory
URLClassLoader ucl = new URLClassLoader(urls);
Object o= ucl.loadClass("test").newInstance();
o.getClass().getMethod("main").invoke(o);
}
public static void main(String[] args) {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
while(true){
try {
String str = br.readLine(); //This can return 'a = 5;','b = "Text";' or 'pckg.example.MyClass.run(5);'
if(str == null)
return;
runCode(str); //How would I do this?
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
//command line
> System.out.println("hello");
hello
> System.out.println(3+2+3+4+5+2);
19
> for(int i = 0; i < 10; i++) {System.out.println(i);}
0
1
2
3
4
5
6
7
8
9
With the SimpleJavaFileObject you could actually avoid using a file, as shown here, but the syntax seems a bit cumbersome so I just opted for a file in the current working directory.
EDIT: Convert String to Code offers a similar approach but it's not fully fleshed out
If the code is in JavaScript then you can run it with JavaScript engine:
Object res = new ScriptEngineManager().getEngineByName("js").eval(str);
JavaScript engine is part of Java SE since 1.6. See this guide http://download.java.net/jdk8/docs/technotes/guides/scripting/programmer_guide/index.html for details
You can use the Java scripting API which is located in the Package javax.script. There you can include several scripting languages like bsh for example.
You can find a programmer's guide on the web page of Oracle.
Rhino, which is some kind of JavaScript is already included with the Oracle JVM.
For this you may want to look into Java Compiler API. I haven't studied much as to how this works, but it allows you to load a java file, compile and load the class in an already running system. Maybe it can be repurposed into accepting input from console.
For a general compiler you could use Janino which will allow you to compile and run Java code. The expression evaluator may help with your example.
If you are just looking to evaluate expressions while debugging then Eclispe has the Display view which allows you to execute expressions. See this question.
I'm a Java programer from China, recently I found a strange thing that the Windows console (eg. cmd.exe) seems to be able to display the characters that are not supported by current Code Page.
Could someone please tell me why?
There is example code and test result below.
import java.io.*;
import java.nio.charset.Charset;
public class EncodingTest {
public static void main(String[] args) {
System.out.println("jvm default charset:" + Charset.defaultCharset());
System.out.println(System.getProperty("file.encoding"));
PrintStream ps = new PrintStream(System.out, true);
ps.println("PrintStream测试");
System.out.println("测试哦，就是要测试啊啊");
System.out.println("中文测试");
System.out.println("--------------");
}
}
and here is screenshot of test result:
Screenshot
I have a problem. I wrote this code that reads a string from a txt file and I exported with the first method a int while the second one particular string. This method is already running but I have used the apache library, now I wanted to rewrite it in Java standard libraries. I have tried this, but I have had problems. Could someone help me? Thank you very much.
package ausiliare;
import java.io.File;
import java.io.IOException;
import org.apache.commons.io.*;
public class Read {
public static int getInt() throws IOException {
String content = null;
File folder = new File("C:\\Solution.txt");
content = FileUtils.readFileToString(folder) + "\n";
int outside = Integer.parseInt(content.substring(0,
content.indexOf("[")).trim());
return outside;
}
public static String getString() throws IOException {
String content = null;
File folder = new File("C:\\Solution.txt");
content = FileUtils.readFileToString(folder) + "\n";
String remainingString = content.substring(content.indexOf(" ["),
content.lastIndexOf("]") + 1);
// System.out.println(remainingString);
return remainingString;
}
public static String[] arg() throws IOException {
String[] strArray = getString().split(" ");
// System.out.println(Arrays.toString(strArray));
return strArray;
}
}
Ps: The input file is txt (for example):
50 [8,24,-22] [-8,34,12] [19,14,47] [-49,32,44] [-41,16,-6] [-49,-11,43]
Where the first method extracts the int 50 and the second extraction method extracts the remaining
content = new String(Files.readAllBytes(folder.toPath()),
StandardCharsets.UTF_8);
The missing part is the knowledge of the Files class.
There is a List<String> readAllLines too.
The character set parameter is optional and defaults to the current operating system's encoding - not very portable to other computers.
This question already has answers here:
Java interpreter? [closed]
(10 answers)
Closed 9 years ago.
For debug reasons, I want to be able to run code that is typed in through the console. For example:
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
while(true){
String str = br.readLine(); //This can return 'a = 5;','b = "Text";' or 'pckg.example.MyClass.run(5);'
if(str == null)
return;
runCode(str); //How would I do this?
}
PLEASE DON'T ACTUALLY USE THIS
I was under the assumption you wanted to evaluate a string as Java code, not some scripting engine like Javascript, so
I created this on a whim after reading this, using the compiler API mark mentioned. It's probably very bad practice but it (somewhat) works like you wanted it to. I doubt it'll be much use in debugging since it runs the code in the context of a new class. Sample usage is included at the bottom.
import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
public class main {
public static void runCode(String s) throws Exception{
JavaCompiler jc = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager sjfm = jc.getStandardFileManager(null, null, null);
File jf = new File("test.java"); //create file in current working directory
PrintWriter pw = new PrintWriter(jf);
pw.println("public class test {public static void main(){"+s+"}}");
pw.close();
Iterable fO = sjfm.getJavaFileObjects(jf);
if(!jc.getTask(null,sjfm,null,null,null,fO).call()) { //compile the code
throw new Exception("compilation failed");
}
URL[] urls = new URL[]{new File("").toURI().toURL()}; //use current working directory
URLClassLoader ucl = new URLClassLoader(urls);
Object o= ucl.loadClass("test").newInstance();
o.getClass().getMethod("main").invoke(o);
}
public static void main(String[] args) {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
while(true){
try {
String str = br.readLine(); //This can return 'a = 5;','b = "Text";' or 'pckg.example.MyClass.run(5);'
if(str == null)
return;
runCode(str); //How would I do this?
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
//command line
> System.out.println("hello");
hello
> System.out.println(3+2+3+4+5+2);
19
> for(int i = 0; i < 10; i++) {System.out.println(i);}
0
1
2
3
4
5
6
7
8
9
With the SimpleJavaFileObject you could actually avoid using a file, as shown here, but the syntax seems a bit cumbersome so I just opted for a file in the current working directory.
EDIT: Convert String to Code offers a similar approach but it's not fully fleshed out
If the code is in JavaScript then you can run it with JavaScript engine:
Object res = new ScriptEngineManager().getEngineByName("js").eval(str);
JavaScript engine is part of Java SE since 1.6. See this guide http://download.java.net/jdk8/docs/technotes/guides/scripting/programmer_guide/index.html for details
You can use the Java scripting API which is located in the Package javax.script. There you can include several scripting languages like bsh for example.
You can find a programmer's guide on the web page of Oracle.
Rhino, which is some kind of JavaScript is already included with the Oracle JVM.
For this you may want to look into Java Compiler API. I haven't studied much as to how this works, but it allows you to load a java file, compile and load the class in an already running system. Maybe it can be repurposed into accepting input from console.
For a general compiler you could use Janino which will allow you to compile and run Java code. The expression evaluator may help with your example.
If you are just looking to evaluate expressions while debugging then Eclispe has the Display view which allows you to execute expressions. See this question.
I have generated and compiled a grammar with ANTLR4. VIA the command line I am able to see if there is an error, but I am having issues integrating this parser into a java program successfully. I am able to use ANTLR4 methods as I've added the JAR's to my library in Eclipse, however I am completely unable to retrieve token text or find out if an error is being generated in any sort of meaningful manner. Any help would be appreciated. If I'm being ambiguous by any means, please let me know and I'll delve into more detail.
Looking at previous versions, an equivalent method to something like compilationUnit() might be what I want.
Something like this should work (assuming you generated GeneratedLexer and GeneratedParser from your grammar):
import java.io.FileInputStream;
import java.io.InputStream;
import org.antlr.v4.runtime.ANTLRInputStream;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.tree.ParseTree;
import test.GeneratedLexer;
import test.GeneratedParser;
public class Main {
public static void main(String[] args) throws Exception {
String inputFile = null;
if (args.length > 0) {
inputFile = args[0];
}
InputStream is = System.in;
if (inputFile != null) {
is = new FileInputStream(inputFile);
}
ANTLRInputStream input = new ANTLRInputStream(is);
GeneratedLexer lexer = new GeneratedLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lexer);
GeneratedParser parser = new GeneratedParser(tokens);
ParseTree tree = parser.startRule();
// Do something useful with the tree (e.g. use a visitor if you generated one)
System.out.println(tree.toStringTree(parser));
}
}
You could also use a parser and lexer interpreter if you don't want to pregenerate them from your grammar (or you have a dynamic grammar).