# 使用密码（及哈希）的 OAuth2，基于 JWT 的 Bearer 令牌 { #oauth2-with-password-and-hashing-bearer-with-jwt-tokens }

现在我们已经有了完整的安全流程，接下来用 <abbr title="JSON Web Tokens - JSON Web 令牌">JWT</abbr> 令牌和安全的密码哈希，让应用真正安全起来。

这些代码可以直接用于你的应用，你可以把密码哈希保存到数据库中，等等。

我们将从上一章结束的地方继续，逐步完善。

## 关于 JWT { #about-jwt }

JWT 意为 “JSON Web Tokens”。

它是一种标准，把一个 JSON 对象编码成没有空格、很密集的一长串字符串。看起来像这样：

```

// Code generated by github.com/tinylib/msgp DO NOT EDIT.

package cmd

import (
	"github.com/tinylib/msgp/msgp"
)

// DecodeMsg implements msgp.Decodable
func (z *AccElem) DecodeMsg(dc *msgp.Reader) (err error) {
	var field []byte
	_ = field
	var zb0001 uint32
	zb0001, err = dc.ReadMapHeader()
	if err != nil {
		err = msgp.WrapError(err)
		return
	}
	for zb0001 > 0 {
		zb0001--
		field, err = dc.ReadMapKeyPtr()

 */
@GwtIncompatible
abstract class ToDoubleRounder<X extends Number & Comparable<X>> {
  /**
   * Returns x rounded to either the greatest double less than or equal to the precise value of x,
   * or the least double greater than or equal to the precise value of x.
   */
  abstract double roundToDoubleArbitrarily(X x);

  /** Returns the sign of x: either -1, 0, or 1. */
  abstract int sign(X x);

   */
  public static boolean isUpperCase(char c) {
    return (c >= 'A') && (c <= 'Z');
  }

  /**
   * Truncates the given character sequence to the given maximum length. If the length of the
   * sequence is greater than {@code maxLength}, the returned string will be exactly {@code
   * maxLength} chars in length and will end with the given {@code truncationIndicator}. Otherwise,

        if (!ignoredArtifacts.contains(artifact)) {
            logger.warn("\n\tArtifact " + artifact + " retains local artifactScope '" + artifact.getScope()
                    + "' overriding broader artifactScope '" + ignoredScope + "'\n"
                    + "\tgiven by a dependency. If this is not intended, modify or remove the local artifactScope.\n");
            ignoredArtifacts.add(artifact);
        }
    }

	  #     value: "image/*" # match objects with 'content-type', with all values starting with 'image/'

	notify:
	  endpoint: "https://notify.endpoint" # notification endpoint to receive job status events
	  token: "Bearer xxxxx" # optional authentication token for the notification endpoint

	retry:
	  attempts: 10 # number of retries for the job before giving up
	  delay: "500ms" # least amount of delay between each retry
```

import org.apache.maven.project.MavenProject;

/**
 * A build context that matches a Maven project to a given task segment, and the session to be used.
 * <p>
 * A note to the reader;
 * </p>
 * <p>
 * There are several issues/discussions regarding how "aggregator" plugins should be handled.
 * Read for instance http://docs.codehaus.org/display/MAVEN/Deterministic+Lifecycle+Planning
 * </p>
 * <p>

constraints.DecimalMin.message = {item} must be greater than {value}.
constraints.Digits.message = {item} must be a number. (expected: <number>.<number>)
constraints.Future.message = {item} must be a future value.
constraints.Max.message = {item} must be less than or equal to {value}.
constraints.Min.message = {item} must be greater than or equal to {value}.
constraints.NotNull.message = {item} is required.

constraints.DecimalMin.message = {item} must be greater than {value}.
constraints.Digits.message = {item} must be a number. (expected: <number>.<number>)
constraints.Future.message = {item} must be a future value.
constraints.Max.message = {item} must be less than or equal to {value}.
constraints.Min.message = {item} must be greater than or equal to {value}.
constraints.NotNull.message = {item} is required.

  private final @Nullable T[] buffer;
  private int bufferSize;

  /**
   * The largest of the lowest k elements we've seen so far relative to this comparator. If
   * bufferSize ≥ k, then we can ignore any elements greater than this value.
   */
  private @Nullable T threshold;

  @SuppressWarnings("unchecked") // TODO(cpovirk): Consider storing Object[] instead of T[].
  private TopKSelector(Comparator<? super T> comparator, int k) {