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Java的MoreSuppliers工具類方法解析

更新時(shí)間：2024年01月16日 08:50:27 作者：加油當(dāng)當(dāng)

這篇文章主要介紹了Java的MoreSuppliers工具類方法解析,MoreSuppliers類是一個(gè)Java工具類,它提供了一些增強(qiáng)的Supplier函數(shù),使得Supplier執(zhí)行的結(jié)果可以被緩存,真正的調(diào)用只執(zhí)行一次,需要的朋友可以參考下

MoreSuppliers工具類

MoreSuppliers類是一個(gè)Java工具類，它提供了一些增強(qiáng)的Supplier函數(shù)，使得Supplier執(zhí)行的結(jié)果可以被緩存，真正的調(diào)用只執(zhí)行一次。

public static <T> CloseableSupplier<T> lazy(Supplier<T> delegate)：

這個(gè)方法返回一個(gè)懶加載的提供器，首次獲取值時(shí)通過delegate加載值，并緩存這個(gè)值，在后續(xù)獲取時(shí)直接返回這個(gè)緩存的值。這個(gè)方法的使用場景是當(dāng)你有一個(gè)計(jì)算成本較高或者IO操作的Supplier，并且你希望只執(zhí)行一次這個(gè)操作，然后緩存結(jié)果以供后續(xù)使用。

示例：

Supplier<String> expensiveOperation = () -> {
    // Some expensive operation...
    return "result";
};
Supplier<String> lazySupplier = MoreSuppliers.lazy(expensiveOperation);
String result = lazySupplier.get();  // The expensive operation is performed here.
String cachedResult = lazySupplier.get();  // The cached result is returned here.

public static <T> CloseableSupplier<T> lazy(Supplier<T> delegate, boolean resetAfterClose)：

這個(gè)方法和上一個(gè)方法類似，但是它允許在關(guān)閉提供器返回的資源后，是否釋放緩存的對象。這個(gè)方法的使用場景是當(dāng)你的Supplier返回的是一個(gè)需要關(guān)閉的資源，比如一個(gè)數(shù)據(jù)庫連接，你希望在關(guān)閉這個(gè)資源后，下次調(diào)用get()方法時(shí)重新獲取一個(gè)新的資源。

示例：

Supplier<Connection> connectionSupplier = () -> {
    // Get a connection from the database...
    return connection;
};
CloseableSupplier<Connection> lazySupplier = MoreSuppliers.lazy(connectionSupplier, true);
Connection connection = lazySupplier.get();  // The connection is obtained here.
lazySupplier.tryClose(Connection::close);  // The connection is closed here.
Connection newConnection = lazySupplier.get();  // A new connection is obtained here.

public static <T, X extends Throwable> CloseableThrowableSupplier<T, X> lazyEx(ThrowableSupplier<T, X> delegate)：

這個(gè)方法返回一個(gè)懶加載的提供器，支持異常類型聲明。這個(gè)方法的使用場景是當(dāng)你的Supplier可能拋出一個(gè)異常，你希望這個(gè)異常能被正確地傳播出去。

示例：

ThrowableSupplier<String, IOException> ioOperation = () -> {
    // Some IO operation...
    return "result";
};
ThrowableSupplier<String, IOException> lazySupplier = MoreSuppliers.lazyEx(ioOperation);
try {
    String result = lazySupplier.get();  // The IO operation is performed here.
} catch (IOException e) {
    // Handle the exception...
}

public static <T, X extends Throwable> CloseableThrowableSupplier<T, X> lazyEx(ThrowableSupplier<T, X> delegate, boolean resetAfterClose)：

這個(gè)方法和上一個(gè)方法類似，但是它允許在關(guān)閉提供器返回的資源后，是否釋放緩存的對象。這個(gè)方法的使用場景是當(dāng)你的Supplier返回的是一個(gè)需要關(guān)閉的資源并且可能拋出一個(gè)異常，你希望在關(guān)閉這個(gè)資源后，下次調(diào)用get()方法時(shí)重新獲取一個(gè)新的資源，并且異常能被正確地傳播出去。

示例：

ThrowableSupplier<Connection, SQLException> connectionSupplier = () -> {
    // Get a connection from the database...
    return connection;
};
CloseableThrowableSupplier<Connection, SQLException> lazySupplier = MoreSuppliers.lazyEx(connectionSupplier, true);
try {
    Connection connection = lazySupplier.get();  // The connection is obtained here.
    lazySupplier.tryClose(Connection::close);  // The connection is closed here.
    Connection newConnection = lazySupplier.get();  // A new connection is obtained here.
} catch (SQLException e) {
    // Handle the exception...
}

public static <T> AsyncSupplier<T> asyncLazyEx(Supplier<T> delegate, Supplier<T> pendingSupplier, String threadName)：

這個(gè)方法返回一個(gè)異步加載的提供器，通過異步線程來完成初始化操作，支持超時(shí)。當(dāng)超過指定的時(shí)間沒有獲取初始值成功時(shí)，使用pendingSupplier提供的值作為托底。這個(gè)方法的使用場景是當(dāng)你的Supplier需要花費(fèi)較長的時(shí)間來獲取值，你希望這個(gè)操作能在一個(gè)單獨(dú)的線程中進(jìn)行，而主線程可以繼續(xù)執(zhí)行其他任務(wù)。

示例：

Supplier<String> slowOperation = () -> {
    // Some slow operation...
    return "result";
};
Supplier<String> fallback = () -> "fallback";
AsyncSupplier<String> asyncSupplier = MoreSuppliers.asyncLazyEx(slowOperation, fallback, "InitThread");
String result = asyncSupplier.get(Duration.ofSeconds(5));  // The slow operation is performed in a separate thread. If it takes more than 5 seconds, the fallback value is returned.

public static <T> AsyncSupplier<T> asyncLazyEx(Supplier<T> delegate, String threadName)：

這個(gè)方法和上一個(gè)方法類似，但是它沒有提供托底的Supplier，如果異步初始化值超時(shí)，它將返回null。

示例：

Supplier<String> slowOperation = () -> {
    // Some slow operation...
    return "result";
};
AsyncSupplier<String> asyncSupplier = MoreSuppliers.asyncLazyEx(slowOperation, "InitThread");
String result = asyncSupplier.get(Duration.ofSeconds(5));  // The slow operation is performed in a separate thread. If it takes more than 5 seconds, null is returned.

public static <T> AsyncSupplier<T> asyncLazyEx(Supplier<T> delegate)：

這個(gè)方法和上一個(gè)方法類似，但是它沒有指定執(zhí)行初始化操作的線程名稱。

示例：

Supplier<String> slowOperation = () -> {
    // Some slow operation...
    return "result";
};
AsyncSupplier<String> asyncSupplier = MoreSuppliers.asyncLazyEx(slowOperation);
String result = asyncSupplier.get(Duration.ofSeconds(5));  // The slow operation is performed in a separate thread. If it takes more than 5 seconds, null is returned.

CloseableSupplier<T>：

這是一個(gè)可關(guān)閉的Supplier實(shí)現(xiàn)，支持通過tryClose(ThrowableConsumer<T, X>closer)方法關(guān)閉提供器返回的資源。

示例：

CloseableSupplier<Connection> connectionSupplier = MoreSuppliers.lazy(() -> {
    // Get a connection from the database...
    return connection;
}, true);
Connection connection = connectionSupplier.get();  // The connection is obtained here.
connectionSupplier.tryClose(Connection::close);  // The connection is closed here.

CloseableThrowableSupplier<T, X>：

這是一個(gè)可關(guān)閉的Supplier實(shí)現(xiàn)，支持異常類型聲明，通過tryClose(ThrowableConsumer<T, X> closer)方法關(guān)閉提供器返回的資源。

示例：

CloseableThrowableSupplier<Connection, SQLException> connectionSupplier = MoreSuppliers.lazyEx(() -> {
 
    // Get a connection from the database...
 
    return connection;
 
}, true);
 
try {
 
    Connection connection = connectionSupplier.get();  // The connection is obtained here.
 
    connectionSupplier.tryClose(Connection::close);  // The connection is closed here.
 
} catch (SQLException e) {
 
    // Handle the exception...
 
}

AsyncSupplier<T>：

這是一個(gè)異步加載的Supplier實(shí)現(xiàn)，通過異步線程來完成初始化操作，支持超時(shí)。當(dāng)超過指定的時(shí)間沒有獲取初始值成功時(shí)，使用pendingSupplier提供的值作為托底。

示例：

Supplier<String> slowOperation = () -> {
    // Some slow operation...
    return "result";
};
Supplier<String> fallback = () -> "fallback";
AsyncSupplier<String> asyncSupplier = MoreSuppliers.asyncLazyEx(slowOperation, fallback, "InitThread");
String result = asyncSupplier.get(Duration.ofSeconds(5));  // The slow operation is performed in a separate thread. If it takes more than 5 seconds, the fallback value is returned.

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