Question

我有一个生成java类并写入.java文件的方法。如何在这个方法上编写单元测试，以确保写入文件的字符串格式是标准的java类格式。

例如：我应该检查它是否有包装声明应检查包是否在类声明之前打开和关闭括号......

Answer 1

这是一个可用于查找Java文件中的编译错误的方法，如果没有生成错误，那么它就是一个完全有效的Java类。

import java.io.File;
import java.io.IOException;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

public class TestMain {

    public static void main(String[] args) {
        List<File> sourceList = Arrays.asList(Paths.get("MyJavaClass.java").toFile());
        List<String> errorList = new TestMain().compile(sourceList);
        if(errorList.size() == 0) {
            System.out.println("No error found, perfectly valid java class");
        } else {
            errorList.forEach(System.out::println);
        }
    }

    public List<String> compile (List<File> javaFileList) {
        System.out.println("Started compilation");
        List<String> errorList = new ArrayList<String>();
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

        DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
        StandardJavaFileManager fileManager = compiler.getStandardFileManager(
                diagnostics, null, null);

        Iterable<? extends JavaFileObject> compilationUnits = fileManager
                .getJavaFileObjectsFromFiles(javaFileList);
        compiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits)
                .call();

        for (Diagnostic<? extends JavaFileObject> diagnostic : diagnostics
                .getDiagnostics()) {
            String diagnosticMessage = String.format("Error on line %d in %s%n",
                    diagnostic.getLineNumber(), diagnostic.getSource().toUri() + " : \n\t" + diagnostic.getMessage(null));

            /*Following gives out of box good message, but I used above to show the custom use of diagnostic
             * String diagnosticMessage = diagnostic.toString();*/

            errorList.add(diagnosticMessage);
        }
        try {
            fileManager.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return errorList;
    }
}

取自Best way to process/handle Error stream messages

Answer 2

如果你只想检查它是否是一个有效的Java类（可以编译），你可以试试。

 try {
            Class<?> clazz = MyTest.class.getClassLoader().loadClass("TargetClass");
            clazz.newInstance();
            } catch (Throwable e) { // Not a good idea to catch error, for test purpose only.
                if(e instanceof Error && e.getMessage().contains("Unresolved compilation problems")){
                    Assert.fail("Invalid class");
                }
            }

您可能需要致电＆＃34; javac＆＃34;进程（请参阅how to compile & run java program in another java program?）以确保在运行此测试检查之前TargetClass.class可用。

测试返回的字符串是否具有java类

2 个答案: