com.google.common.base.Converter类的使用及代码示例

x33g5p2x  于2022-01-18 转载在 其他  
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本文整理了Java中com.google.common.base.Converter类的一些代码示例，展示了Converter类的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Converter类的具体详情如下：
包路径：com.google.common.base.Converter
类名称：Converter

Converter介绍

[英]A function from A to B with an associated reverse function from Bto A; used for converting back and forth between different representations of the same information.

Invertibility

The reverse operation may be a strict inverse (meaning that converter.reverse().convert(converter.convert(a)).equals(a) is always true). However, it is very common (perhaps more common) for round-trip conversion to be lossy. Consider an example round-trip using com.google.common.primitives.Doubles#stringConverter:

  1. stringConverter().convert("1.00") returns the Double value 1.0
  2. stringConverter().reverse().convert(1.0) returns the string "1.0" -- not the same string ( "1.00") we started with

Note that it should still be the case that the round-tripped and original objects are similar.

Nullability

A converter always converts null to null and non-null references to non-null references. It would not make sense to consider null and a non-null reference to be "different representations of the same information", since one is distinguishable from missing information and the other is not. The #convert method handles this null behavior for all converters; implementations of #doForward and #doBackward are guaranteed to never be passed null, and must never return null.

Common ways to use

Getting a converter:

  • Use a provided converter implementation, such as Enums#stringConverter, com.google.common.primitives.Ints#stringConverter or the #reverse views of these.
  • Convert between specific preset values using com.google.common.collect.Maps#asConverter. For example, use this to create a "fake" converter for a unit test. It is unnecessary (and confusing) to mock the Converter type using a mocking framework.
  • Extend this class and implement its #doForward and #doBackward methods.
  • Java 8 users: you may prefer to pass two lambda expressions or method references to the #from factory method.

Using a converter:

  • Convert one instance in the "forward" direction using converter.convert(a).
  • Convert multiple instances "forward" using converter.convertAll(as).
  • Convert in the "backward" direction using converter.reverse().convert(b) or converter.reverse().convertAll(bs).
  • Use converter or converter.reverse() anywhere a java.util.function.Function is accepted (for example java.util.stream.Stream#map).
  • Do not call #doForward or #doBackward directly; these exist only to be overridden.

Example

return new Converter<Integer, String>() { 
protected String doForward(Integer i) { 
return Integer.toHexString(i); 
} 
protected Integer doBackward(String s) { 
return parseUnsignedInt(s, 16); 
} 
};

An alternative using Java 8:

return Converter.from(

[中]从A到B的功能，以及从B到A的相关反向功能；用于在相同信息的不同表示之间来回转换。
####可逆性
反向操作可能是严格的反向操作（即converter.reverse（）。转换（convert.convert（a））。等于（a）总是正确的）。然而，往返转换有损是非常常见的（可能更常见）。考虑使用COM的往返示例。谷歌。常见的原语。双列#stringConverter：
1.stringConverter（）。convert（“1.00”）返回双精度值1.0
1.stringConverter（）。反向（）。convert（1.0）返回字符串“1.0”--与我们开始使用的字符串（“1.00”）不同
请注意，往返对象和原始对象应该是相似的。
####无效性
转换器总是将空引用转换为空引用，将非空引用转换为非空引用。考虑NULL和非空引用是“相同信息的不同表示”，这是没有意义的，因为一个可以区别于丢失的信息，而另一个不是。#convert方法处理所有转换器的这种空行为；#doForward和#doBackward的实现保证永远不会传递null，并且永远不能返回null。
####常用的使用方法
获取转换器：
*使用提供的转换器实现，例如Enums#stringConverter、com。谷歌。常见的原语。Ints#stringConverter或其#反向视图。
*使用com在特定预设值之间转换。谷歌。常见的收集地图是一个转换器。例如，使用它为单元测试创建一个“假”转换器。使用模拟框架模拟转换器类型是不必要的（而且容易混淆）。
*扩展此类并实现其#doForward和#doBackward方法。
*Java8用户：您可能更愿意将两个lambda表达式或方法引用传递给#from factory方法。
使用转换器：
*使用转换器在“正向”方向转换一个实例。转换（a）。
*使用转换器“正向”转换多个实例。convertAll（as）。
*使用转换器在“向后”方向进行转换。反向（）。转换（b）或转换器。反向（）。康沃尔特（bs）。
*使用转换器或转换器。reverse（）在java中的任何位置。util。作用函数被接受（例如java.util.stream.stream#map）。
*不要直接呼叫#doForward或#doBackward；这些存在只是为了被覆盖。
####范例

return new Converter<Integer, String>() { 
protected String doForward(Integer i) { 
return Integer.toHexString(i); 
} 
protected Integer doBackward(String s) { 
return parseUnsignedInt(s, 16); 
} 
};

使用Java 8的替代方案：

return Converter.from(

代码示例

代码示例来源：origin: google/guava

public void testStringConverter_reverse() {
 Converter<String, Integer> converter = Ints.stringConverter();
 assertEquals("1", converter.reverse().convert(1));
 assertEquals("0", converter.reverse().convert(0));
 assertEquals("-1", converter.reverse().convert(-1));
 assertEquals("255", converter.reverse().convert(0xff));
 assertEquals("255", converter.reverse().convert(0xFF));
 assertEquals("-255", converter.reverse().convert(-0xFF));
 assertEquals("438", converter.reverse().convert(0666));
}

代码示例来源：origin: google/guava

@Override
public boolean equals(@Nullable Object object) {
 if (object instanceof ConverterComposition) {
  ConverterComposition<?, ?, ?> that = (ConverterComposition<?, ?, ?>) object;
  return this.first.equals(that.first) && this.second.equals(that.second);
 }
 return false;
}

代码示例来源：origin: google/guava

@Override
@Nullable
A correctedDoBackward(@Nullable C c) {
 return first.correctedDoBackward(second.correctedDoBackward(c));
}

代码示例来源：origin: google/guava

public void testIdentityConverter() {
 Converter<String, String> stringIdentityConverter = Converter.identity();
 assertSame(stringIdentityConverter, stringIdentityConverter.reverse());
 assertSame(STR_TO_LONG, stringIdentityConverter.andThen(STR_TO_LONG));
 assertSame(STR_VAL, stringIdentityConverter.convert(STR_VAL));
 assertSame(STR_VAL, stringIdentityConverter.reverse().convert(STR_VAL));
 assertEquals("Converter.identity()", stringIdentityConverter.toString());
 assertSame(Converter.identity(), Converter.identity());
}

代码示例来源：origin: google/guava

public void testConverter() {
 assertEquals(LONG_VAL, STR_TO_LONG.convert(STR_VAL));
 assertEquals(STR_VAL, STR_TO_LONG.reverse().convert(LONG_VAL));
 Iterable<Long> convertedValues = STR_TO_LONG.convertAll(STRINGS);
 assertEquals(LONGS, ImmutableList.copyOf(convertedValues));
}

代码示例来源：origin: com.google.guava/guava-jdk5

@Override
@Nullable
C correctedDoForward(@Nullable A a) {
 return second.correctedDoForward(first.correctedDoForward(a));
}

代码示例来源：origin: com.google.guava/guava-jdk5

@Override
@Nullable
A correctedDoBackward(@Nullable C c) {
 return first.correctedDoBackward(second.correctedDoBackward(c));
}

代码示例来源：origin: com.google.guava/guava-jdk5

@Override
public boolean equals(@Nullable Object object) {
 if (object instanceof ConverterComposition) {
  ConverterComposition<?, ?, ?> that = (ConverterComposition<?, ?, ?>) object;
  return this.first.equals(that.first)
    && this.second.equals(that.second);
 }
 return false;
}

代码示例来源：origin: com.google.guava/guava-jdk5

/**
 * @deprecated Provided to satisfy the {@code Function} interface; use {@link #convert} instead.
 */
@Deprecated
@Override
@Nullable
public final B apply(@Nullable A a) {
 return convert(a);
}

代码示例来源：origin: org.fcrepo/fcrepo-kernel-modeshape

/**
   * Get the membership resource relation asserted by the container
   * @param parent resource with relations
   * @return Node of member
   * @throws RepositoryException on error
   */
  private Node getMemberResource(final FedoraResource parent) throws RepositoryException {
    final Node membershipResource;

    if (parent.hasProperty(LDP_MEMBER_RESOURCE)) {
      final Property memberResource = getJcrNode(parent).getProperty(LDP_MEMBER_RESOURCE);

      if (REFERENCE_TYPES.contains(memberResource.getType())) {
        membershipResource = nodeConverter().convert(memberResource.getNode()).asNode();
      } else {
        membershipResource = createURI(memberResource.getString());
      }
    } else {
      membershipResource = uriFor(parent);
    }

    return membershipResource;
  }
}

代码示例来源：origin: org.fcrepo/fcrepo-http-api

/**
 * This is a helper method for using the idTranslator to convert this resource into an associated Jena Node.
 *
 * @param resource to be converted into a Jena Node
 * @return the Jena node
 */
protected Node asNode(final FedoraResource resource) {
  return translator().reverse().convert(resource).asNode();
}

代码示例来源：origin: org.fcrepo/fcrepo-kernel-modeshape

@Override
public String asString(final Resource subject) {
  if (!inDomain(subject)) {
    return null;
  }
  final String path = subject.getURI().substring(resourceNamespace.length() - 1);
  final String absPath = forward.convert(path);
  if (absPath.isEmpty()) {
    return "/";
  }
  return absPath;
}

代码示例来源：origin: org.fcrepo/fcrepo-http-api

private static void addContentStatements(final IdentifierConverter<Resource,FedoraResource> idTranslator,
                     final FedoraBinary resource,
                     final Model model) {
  // fcr:fixity
  final Resource subject = idTranslator.reverse().convert(resource);
  model.add(subject, HAS_FIXITY_SERVICE, createResource(subject.getURI() +
      "/fcr:fixity"));
}

代码示例来源：origin: org.fcrepo/fcrepo-kernel-modeshape

@Override
public RdfStream getTriples(final IdentifierConverter<Resource, FedoraResource> idTranslator,
              final Set<? extends TripleCategory> contexts) {
  final FedoraResource described = getOriginalResource().getDescribedResource();
  final org.apache.jena.graph.Node describedNode = idTranslator.reverse().convert(described).asNode();
  final String resourceUri = idTranslator.reverse().convert(this).getURI();
  Stream<Triple> triples = contexts.stream()
      .filter(contextMap::containsKey)
      .map(x -> contextMap.get(x).apply(this).apply(idTranslator).apply(contexts.contains(MINIMAL)))
      .reduce(empty(), Stream::concat)
      .map(t -> mapSubject(t, resourceUri, describedNode));
  // if a memento, convert subjects to original resource and object references from referential integrity
  // ignoring internal URL back the original external URL.
  if (isMemento()) {
    final IdentifierConverter<Resource, FedoraResource> internalIdTranslator =
        new InternalIdentifierTranslator(getSession());
    triples = triples.map(convertMementoReferences(idTranslator, internalIdTranslator));
  }
  return new DefaultRdfStream(idTranslator.reverse().convert(described).asNode(), triples);
}

代码示例来源：origin: google/guava

/**
 * @deprecated Provided to satisfy the {@code Function} interface; use {@link #convert} instead.
 */
@Deprecated
@Override
@CanIgnoreReturnValue
public final @Nullable B apply(@Nullable A a) {
 return convert(a);
}

代码示例来源：origin: org.fcrepo/fcrepo-http-api

@Override
protected void addResourceHttpHeaders(final FedoraResource resource) {
  super.addResourceHttpHeaders(resource);
  if (session.isBatchSession()) {
    final String canonical = translator().reverse()
        .convert(resource)
        .toString()
        .replaceFirst("/tx:[^/]+", "");
    servletResponse.addHeader(LINK, "<" + canonical + ">;rel=\"canonical\"");
  }
  addExternalContentHeaders(resource);
}

代码示例来源：origin: SmartDataAnalytics/jena-sparql-api

@Override
  protected R doBackward(J b) {
    Node node = converter.reverse().convert(b);//nodeMapper.toNode(b);
    RDFNode tmp = model.asRDFNode(node);
    R result = tmp.as(rdfViewClass);
    return result;
  }    
}

代码示例来源：origin: google/guava

public void testSerialization_andThen() {
 Converter<String, Long> converterA = Longs.stringConverter();
 Converter<Long, String> reverseConverter = Longs.stringConverter().reverse();
 Converter<String, String> composedConverter = converterA.andThen(reverseConverter);
 SerializableTester.reserializeAndAssert(composedConverter);
}

代码示例来源：origin: google/guava

@Override
@Nullable
C correctedDoForward(@Nullable A a) {
 return second.correctedDoForward(first.correctedDoForward(a));
}

代码示例来源：origin: Nextdoor/bender

@Override
@Nullable
C correctedDoForward(@Nullable A a) {
 return second.correctedDoForward(first.correctedDoForward(a));
}

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