org.springframework.util

## 类 PropertyPlaceholderHelper

- java.lang.Object
- - org.springframework.util.PropertyPlaceholderHelper

-     public class PropertyPlaceholderHelper
      extends Object

  Utility class for working with Strings that have placeholder values in them. A placeholder takes the form `${name}`. Using `PropertyPlaceholderHelper` these placeholders can be substituted for user-supplied values.

  Values for substitution can be supplied using a `Properties` instance or using a `PropertyPlaceholderHelper.PlaceholderResolver`.

  从以下版本开始:
    3.0
  作者:
    Juergen Hoeller, Rob Harrop

- - ### 嵌套类概要

    嵌套类
    限定符和类型 | 类和说明
    --- | ---
    `static interface` | `PropertyPlaceholderHelper.PlaceholderResolver` Strategy interface used to resolve replacement values for placeholders contained in Strings.

  - ### 构造器概要

    构造器
    构造器和说明
    `PropertyPlaceholderHelper(String placeholderPrefix, String placeholderSuffix)` Creates a new `PropertyPlaceholderHelper` that uses the supplied prefix and suffix.
    `PropertyPlaceholderHelper(String placeholderPrefix, String placeholderSuffix, String valueSeparator, boolean ignoreUnresolvablePlaceholders)` Creates a new `PropertyPlaceholderHelper` that uses the supplied prefix and suffix.

  - ### 方法概要

    所有方法 实例方法 具体方法
    限定符和类型 | 方法和说明
    --- | ---
    `protected String` | `parseStringValue(String value, PropertyPlaceholderHelper.PlaceholderResolver placeholderResolver, Set<String> visitedPlaceholders)`
    `String` | `replacePlaceholders(String value, Properties properties)` Replaces all placeholders of format `${name}` with the corresponding property from the supplied `Properties`.
    `String` | `replacePlaceholders(String value, PropertyPlaceholderHelper.PlaceholderResolver placeholderResolver)` Replaces all placeholders of format `${name}` with the value returned from the supplied `PropertyPlaceholderHelper.PlaceholderResolver`.

    - ### 从类继承的方法 java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### 构造器详细资料

    - #### PropertyPlaceholderHelper

          public PropertyPlaceholderHelper(String placeholderPrefix,
                                           String placeholderSuffix)

      Creates a new `PropertyPlaceholderHelper` that uses the supplied prefix and suffix. Unresolvable placeholders are ignored.
      参数:
        `placeholderPrefix` - the prefix that denotes the start of a placeholder
        `placeholderSuffix` - the suffix that denotes the end of a placeholder

    - #### PropertyPlaceholderHelper

          public PropertyPlaceholderHelper(String placeholderPrefix,
                                           String placeholderSuffix,
                                           @Nullable
                                           String valueSeparator,
                                           boolean ignoreUnresolvablePlaceholders)

      Creates a new `PropertyPlaceholderHelper` that uses the supplied prefix and suffix.
      参数:
        `placeholderPrefix` - the prefix that denotes the start of a placeholder
        `placeholderSuffix` - the suffix that denotes the end of a placeholder
        `valueSeparator` - the separating character between the placeholder variable and the associated default value, if any
        `ignoreUnresolvablePlaceholders` - indicates whether unresolvable placeholders should be ignored (`true`) or cause an exception (`false`)

  - ### 方法详细资料

    - #### replacePlaceholders

          public String replacePlaceholders(String value,
                                            Properties properties)

      Replaces all placeholders of format `${name}` with the corresponding property from the supplied `Properties`.
      参数:
        `value` - the value containing the placeholders to be replaced
        `properties` - the `Properties` to use for replacement
      返回:
        the supplied value with placeholders replaced inline

    - #### replacePlaceholders

          public String replacePlaceholders(String value,
                                            PropertyPlaceholderHelper.PlaceholderResolver placeholderResolver)

      Replaces all placeholders of format `${name}` with the value returned from the supplied `PropertyPlaceholderHelper.PlaceholderResolver`.
      参数:
        `value` - the value containing the placeholders to be replaced
        `placeholderResolver` - the `PlaceholderResolver` to use for replacement
      返回:
        the supplied value with placeholders replaced inline

    - #### parseStringValue

          protected String parseStringValue(String value,
                                            PropertyPlaceholderHelper.PlaceholderResolver placeholderResolver,
                                            Set<String> visitedPlaceholders)