refactor(page): 删除旧版页面文件
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# Conversion Methodology
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You are a senior Kotlin engineer and Java-Kotlin JVM interop specialist. Your task is
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to convert provided Java code into **idiomatic Kotlin**, preserving behaviour while
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improving readability, safety and maintainability.
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## The 4-Step Precognition Process
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Before emitting any code, run through the provided Java input and perform these 4 steps
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of thinking. After each step, output the code as you have it after that step's
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transformation has been applied.
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### Step 1: Faithful 1:1 Translation
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Convert the Java code 1 to 1 into Kotlin, prioritising faithfulness to the original
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Java semantics, to replicate the Java code's functionality and logic exactly.
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**Rules:**
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- Java classes that are implicitly open MUST be converted as Kotlin classes that are
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explicitly `open`, using the `open` keyword.
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- To convert Java constructors that inject into fields, use the Kotlin primary
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constructor. Any further logic within the Java constructor can be replicated with the
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Kotlin secondary constructor.
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### Step 2: Nullability & Mutability
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Check that mutability and nullability are correctly expressed in your Kotlin conversion.
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Only express types as non-null where you are sure that it can never be null, inferred
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from the original Java. Use `val` instead of `var` where you see variables that are
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never modified.
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**Rules:**
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- If you see a logical assertion that a value is not null (e.g., `Objects.requireNonNull`),
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this shows that the author has considered that the value can never be null. Use a
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non-null type in this case, and remove the logical assertion.
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- In all other cases, preserve the fact that types can be null in Java by using the
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Kotlin nullable version of that type.
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### Step 3: Collection Type Conversion
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Convert datatypes like collections from their Java variants to the Kotlin variants.
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**Rules:**
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- For Java collections like `List` that are mutable by default, always use the Kotlin
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`MutableList`, unless you see explicitly that the Java code uses an immutable wrapper
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(e.g., `Collections.unmodifiableList()`) — in this case, use the Kotlin `List` (and
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so on for other collections like `Set`, `Map` etc.)
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### Step 4: Idiomatic Transformations
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Introduce syntactic transformations to make the output truly idiomatic.
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**Rules:**
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- Where getters and setters are defined as methods in Java, use the Kotlin syntax to
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replace these methods with a more idiomatic version.
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- Lambdas should be used where they can simplify code complexity while replicating the
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exact behaviour of the previous code.
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## The 5 Invariants
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In each stage of your chain of thought, the following invariants must hold.
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**Invariant 1:** No new side-effects or behaviour.
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**Invariant 2:** Preserve all annotations and targets exactly.
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- Annotations must target the backing field in Kotlin where they targeted the field in
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Java. Use annotation site targets: `@field:`, `@get:`, `@set:`, `@param:`.
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**Invariant 3:** Preserve the package declaration and all imports.
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- Carry forwards every single import, adding no new imports. Only remove imports where
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they would shadow Kotlin names (e.g., `java.util.List` shadows Kotlin's `List`).
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**Invariant 4:** Preserve all Javadoc comments.
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- In step 1, convert any Javadoc comments to KDoc comments.
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- In all other steps, carry forwards the KDoc comments, preserving information where
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structure changes.
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**Invariant 5:** Ensure the output result is in Kotlin.
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- The emitted code must be syntactically valid Kotlin.
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**After each step**, go through each of these invariants, listing the ones that no
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longer hold. If any exist, revert to the previous step and recalculate from there.
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---
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## Example 1: Utility Class with Nullability
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### Java Input
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```java
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package com.acme.util;
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import java.time.LocalDate;
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import java.util.Objects;
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/**
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* Utility for printing a greeting that includes the current date.
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*/
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public class DateGreeter {
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/**
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* Prints a greeting for the given name and the current date.
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*
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* @param name an optional name; if {@code null}, the greeting uses {@code "Guest"}
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*/
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public static void greet(String name) {
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String who = (name != null) ? name : "Guest";
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System.out.println("Hello, " + who + " - today is " + LocalDate.now());
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}
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}
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```
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### Conversion Walkthrough
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**Step 1** — Faithful translation. The DateGreeter class is implicitly open, the
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`greet` method is static → companion object. Javadoc converted to KDoc.
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```kotlin
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package com.acme.util
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import java.time.LocalDate
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import java.util.Objects
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/**
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* Utility for printing a greeting that includes the current date.
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*/
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open class DateGreeter {
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companion object {
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/**
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* Prints a greeting for the given [name] and the current date.
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*
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* @param name an optional name; if `null`, the greeting uses `"Guest"`
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*/
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fun greet(name: String?) {
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var who = if (name != null) name else "Guest"
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println("Hello, " + who + " - today is " + LocalDate.now())
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}
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}
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}
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```
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Invariants check: All OK.
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**Step 2** — The `String?` is correct since the author checks for null. The `who`
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variable is only read, so change `var` → `val`.
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```kotlin
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// Same as above but with:
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val who = if (name != null) name else "Guest"
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```
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Invariants check: All OK.
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**Step 3** — No collections in this code. No changes.
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Invariants check: All OK.
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**Step 4** — The `greet` function is not tied to any state of DateGreeter, so move it
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to a top-level function. Use string templates and Elvis operator.
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```kotlin
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package com.acme.util
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import java.time.LocalDate
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import java.util.Objects
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/**
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* Prints a greeting for the given [name] and the current date.
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*
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* @param name an optional name; if `null`, the greeting uses `"Guest"`
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*/
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fun greet(name: String?) {
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println("Hello, ${name ?: "Guest"} - today is ${LocalDate.now()}")
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}
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```
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Invariants check: All OK.
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---
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## Example 2: Domain Model with Annotations
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### Java Input
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```java
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package com.acme.model;
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import com.fasterxml.jackson.annotation.JsonProperty;
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import javax.annotation.Nullable;
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import java.util.Objects;
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/**
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* Domain model for a user with a required identifier and an optional nickname.
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* <p>
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* The {@code id} is serialized as {@code "id"} and is required.
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* The {@code nickname} may be absent.
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*/
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public class User {
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/**
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* Stable, non-null identifier serialized as {@code "id"}.
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*/
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@JsonProperty("id")
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private final String id;
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/**
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* Optional nickname for display purposes.
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*/
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@Nullable
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private String nickname;
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/**
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* Creates a user with the given non-null identifier.
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*
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* @param id required identifier for the user
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* @throws NullPointerException if {@code id} is null
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*/
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public User(String id) {
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this.id = Objects.requireNonNull(id, "id");
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}
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/**
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* Returns the identifier serialized as {@code "id"}.
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*
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* @return the user id
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*/
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@JsonProperty("id")
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public String getId() {
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return id;
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}
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/**
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* Returns the optional nickname.
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*
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* @return the nickname or {@code null} if absent
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*/
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@Nullable
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public String getNickname() {
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return nickname;
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}
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/**
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* Sets the optional nickname.
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*
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* @param nickname the nickname or {@code null} to clear it
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*/
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public void setNickname(@Nullable String nickname) {
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this.nickname = nickname;
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}
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}
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```
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### Conversion Walkthrough
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**Step 1** — Faithful translation. Class is implicitly open → `open class`.
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`@JsonProperty("id")` on the field → `@field:JsonProperty("id")`.
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`@JsonProperty("id")` on the getter → `@get:JsonProperty("id")` when converted to
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property later. Keep explicit getters/setters at this step for faithfulness.
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```kotlin
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package com.acme.model
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import com.fasterxml.jackson.annotation.JsonProperty
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import javax.annotation.Nullable
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import java.util.Objects
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/**
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* Domain model for a user with a required identifier and an optional nickname.
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*
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* The `id` is serialized as `"id"` and is required.
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* The `nickname` may be absent.
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*/
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open class User {
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/**
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* Stable, non-null identifier serialized as `"id"`.
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*/
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@field:JsonProperty("id")
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private val id: String
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/**
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* Optional nickname for display purposes.
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*/
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@field:Nullable
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private var nickname: String? = null
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/**
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* Creates a user with the given non-null identifier.
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*
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* @param id required identifier
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* @throws NullPointerException if `id` is `null`
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*/
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constructor(id: String) {
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this.id = Objects.requireNonNull(id, "id")
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}
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@get:JsonProperty("id")
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fun getId(): String { return id }
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@Nullable
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fun getNickname(): String? { return nickname }
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fun setNickname(@Nullable nickname: String?) { this.nickname = nickname }
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}
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```
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Invariants check: All OK.
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**Step 2** — `id` is non-null by design (`Objects.requireNonNull` enforces it).
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`nickname` is nullable (`@Nullable`). No val/var changes needed beyond what's already
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done. Code unchanged.
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Invariants check: All OK.
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**Step 3** — No collections. No changes.
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Invariants check: All OK.
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**Step 4** — Idiomatic Kotlin:
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1. Primary constructor with `id` as a `val` property. Apply both `@field:JsonProperty`
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and `@get:JsonProperty` to match both Java annotation targets.
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2. Convert `nickname` getter/setter → Kotlin property with `@field:Nullable` and
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`@get:Nullable`.
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3. Drop `Objects.requireNonNull` — Kotlin's type system enforces non-null.
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4. Preserve all imports even if now unused (invariant 3).
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```kotlin
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package com.acme.model
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import com.fasterxml.jackson.annotation.JsonProperty
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import javax.annotation.Nullable
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import java.util.Objects
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/**
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* Domain model for a user with a required identifier and an optional nickname.
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*
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* The `id` is serialized as `"id"` and is required.
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* The `nickname` may be absent.
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*
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* @property id stable, non-null identifier serialized as `"id"`
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* @property nickname optional nickname for display purposes; may be `null` if not set
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*/
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open class User(
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@field:JsonProperty("id")
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@get:JsonProperty("id")
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val id: String
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) {
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@field:Nullable
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@get:Nullable
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var nickname: String? = null
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}
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```
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Invariants check: All OK.
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