new: first implementation (#2)

Author: sttk

src/main/java/Sample.java

@@ -0,0 +1,220 @@
+/*
+ * Exc class.
+ * Copyright (C) 2025 Takayuki Sato. All Rights Reserved.
+ */
+package com.github.sttk.errs;
+
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+import java.io.IOException;
+import java.io.NotSerializableException;
+import java.io.InvalidObjectException;
+
+/**
+ * Is the exception class with a reason.
+ * <p>
+ * This class has a record field which indicates a reason for this exception. The class name of the reason record
+ * represents the type of reason, and the fields of the reason record hold the situation where the exception occurred.
+ * <p>
+ * Optionally, this exception class can notify its instance creation to pre-registered exception handlers.
+ * <p>
+ * The example code of creating and throwing an excepton is as follows:
+ *
+ * <pre>{@code
+ * public record FailToDoSomething(String name, int value) {
+ * }
+ *
+ * try {
+ *     throw new Exc(new FailToDoSomething("abc", 123));
+ * } catch (Err e) {
+ *     System.out.println(e.getMessage()); // => "FailToDoSomething { name=abc, value=123 }"
+ * }
+ * }</pre>
+ */
+public final class Exc extends Exception {
+
+    /** The serial version UID. */
+    private static final long serialVersionUID = 260427082865587554L;
+
+    /** The reason for this exception. */
+    private transient Record reason;
+
+    /** The stack trace for the location of occurrence. */
+    private StackTraceElement trace;
+
+    /**
+     * Is the constructor which takes a {@link Record} object indicating the reason for this exception.
+     *
+     * @param reason
+     *            A reason for this exception.
+     */
+    public Exc(final Record reason) {
+        if (reason == null) {
+            throw new IllegalArgumentException("reason is null");
+        }
+        this.reason = reason;
+
+        this.trace = getStackTrace()[0];
+    }
+
+    /**
+     * Is the constructor which takes a {@link Record} object indicating the reason and {@link Throwable} object
+     * indicating the cause for this exception.
+     *
+     * @param reason
+     *            A reason for this exception.
+     * @param cause
+     *            A cause for this exception.
+     */
+    @SuppressWarnings("this-escape")
+    public Exc(final Record reason, final Throwable cause) {
+        super(cause);
+
+        if (reason == null) {
+            throw new IllegalArgumentException("reason is null");
+        }
+        this.reason = reason;
+
+        this.trace = getStackTrace()[0];
+    }
+
+    /**
+     * Gets the reason for this exception. The type of the reason.
+     *
+     * @return The reason for this exception.
+     */
+    public Record getReason() {
+        return this.reason;
+    }
+
+    /**
+     * Returns the message of this exception, that is the reason.
+     *
+     * @return The message of this exception.
+     */
+    @Override
+    public String getMessage() {
+        var rsn = this.reason.toString();
+        var rname = this.reason.getClass().getSimpleName();
+        rsn = rsn.substring(rname.length() + 1, rsn.length() - 1);
+
+        var buf = new StringBuilder(this.reason.getClass().getName());
+        buf.append(" { ").append(rsn).append(" }");
+        return buf.toString();
+    }
+
+    /**
+     * Returns the detail message of this exception, that contains the reason, source file name, line number, and the
+     * cause if provided.
+     *
+     * @return The message of this exception.
+     */
+    @Override
+    public String toString() {
+        var buf = new StringBuilder(getClass().getName());
+        buf.append(" { reason = ").append(getMessage());
+        buf.append(", file = ").append(this.trace.getFileName());
+        buf.append(", line = ").append(this.trace.getLineNumber());
+        if (getCause() != null) {
+            buf.append(", cause = ").append(getCause().toString());
+        }
+        return buf.append(" }").toString();
+    }
+
+    /**
+     * Returns the name of the source file of this exception occurrance.
+     * <p>
+     * This method can return null if this information is unavailable.
+     *
+     * @return The name of the source file of this error occurrence.
+     */
+    public String getFile() {
+        return this.trace.getFileName();
+    }
+
+    /**
+     * Returns the line number of this exception occurrance in the source file.
+     * <p>
+     * This method can return a negative number if this information is unavailable.
+     *
+     * @return The line number of this exception occurrance in the source file.
+     */
+    public int getLine() {
+        return this.trace.getLineNumber();
+    }
+
+    /**
+     * Creates a {@link RuntimeException} object for methods that cannot throw a {@link Exc}.
+     *
+     * @return A {@link RuntimeException} object.
+     */
+    public RuntimeException toRuntimeException() {
+        return new RuntimeExc(this);
+    }
+
+    /**
+     * Writes a serial data of this exception to a stream.
+     * <p>
+     * Since a {@link Record} object is not necessarily serializable, this method will throw a
+     * {@link NotSerializableException} if the {@code reason} field does not inherit {@link Serializable}.
+     *
+     * @param out
+     *            An {@link ObjectOutputStream} to which data is written.
+     *
+     * @throws IOException
+     *             if an I/O error occurs.
+     */
+    private void writeObject(ObjectOutputStream out) throws IOException {
+        if (!(this.reason instanceof Serializable)) {
+            throw new NotSerializableException(this.reason.getClass().getName());
+        }
+        out.defaultWriteObject();
+        out.writeObject(this.reason);
+    }
+
+    /**
+     * Reconstitutes the {@code Exc} instance from a stream and initialize the reason and cause properties when
+     * deserializing. If the reason by deserialization is null or invalid, this method throws
+     * {@link InvalidObjectException}.
+     *
+     * @param in
+     *            An {@link ObjectInputStream} from which data is read.
+     *
+     * @throws IOException
+     *             if an I/O error occurs.
+     * @throws ClassNotFoundException
+     *             if a serialized class cannot be loaded.
+     */
+    private void readObject(ObjectInputStream in) throws ClassNotFoundException, IOException {
+        in.defaultReadObject();
+        this.reason = Record.class.cast(in.readObject());
+
+        if (this.reason == null) {
+            throw new InvalidObjectException("reason is null or invalid.");
+        }
+    }
+}
+
+final class RuntimeExc extends RuntimeException {
+    private static final long serialVersionUID = 4664405757902479929L;
+
+    RuntimeExc(Exc exc) {
+        super(exc);
+    }
+
+    @Override
+    public String getMessage() {
+        return getCause().getMessage();
+    }
+
+    @Override
+    public String toString() {
+        return getClass().getName() + ": " + getCause().toString();
+    }
+
+    @Override
+    public Throwable fillInStackTrace() {
+        return null;
+    }
+}

src/main/java/com/github/sttk/errs/Exc.java

@@ -0,0 +1,15 @@
+/*
+ * Copyright (C) 2024 Takayuki Sato. All Rights Reserved.
+ *
+ * This program is free software under MIT License.
+ * See the file LICENSE in this distribution for more details.
+ */
+
+/**
+ * Provides classes for handling an exception with a reason.
+ * <p>
+ * This package contains the {@code Exc} class which has a record field indicates the reason for the exception.
+ *
+ * @version 0.1
+ */
+package com.github.sttk.errs;

src/main/java/com/github/sttk/errs/package-info.java

@@ -0,0 +1,15 @@
+/*
+ * Copyright (C) 2025 Takayuki Sato. All Rights Reserved.
+ *
+ * This program is free software under MIT License.
+ * See the file LICENSE in this distribution for more details.
+ */
+
+/**
+ * Contains a package which provides the APIs for handling an exception with a reason.
+ *
+ * @version 0.1
+ */
+module com.github.sttk.errs {
+  exports com.github.sttk.errs;
+}

src/main/java/module-info.java

@@ -0,0 +1,41 @@
+{
+  "types": [
+    {
+      "name": "com.github.sttk.errs.Exc"
+    },
+    {
+      "name": "java.io.IOException"
+    },
+    {
+      "name": "java.io.NotSerializableException"
+    },
+    {
+      "name": "java.io.ObjectStreamException"
+    },
+    {
+      "name": "java.lang.Exception"
+    },
+    {
+      "name": "java.lang.RuntimeException"
+    },
+    {
+      "name": "java.lang.StackTraceElement"
+    },
+    {
+      "name": "java.lang.StackTraceElement[]"
+    },
+    {
+      "name": "java.lang.String"
+    },
+    {
+      "name": "java.lang.Throwable"
+    },
+    {
+      "name": "java.util.Collections$EmptyList"
+    }
+  ],
+  "lambdaCapturingTypes":[
+  ],
+  "proxies":[
+  ]
+}