if (log.isTraceEnabled()) {
                    log.trace("Failed to send nameservice request for " + name.name, ioe);
                }
                throw new UnknownHostException(name.name);
            } catch (final IOException ioe) {
                log.info("Failed to send nameservice request for " + name.name, ioe);
                throw new UnknownHostException(name.name);

		files := []file{}
		for {
			hdr, err := r.Next()
			if err == io.EOF {
				break
			}
			if err != nil {
				return
			}
			buf := bytes.NewBuffer(nil)
			if _, err := io.Copy(buf, r); err != nil {
				continue
			}
			files = append(files, file{header: hdr, content: buf.Bytes()})
		}

		// If we were unable to read anything out of the archive don't
		// bother trying to roundtrip it.
		if len(files) == 0 {

与在*路径操作函数*中使用 `Query`、`Path` 、`Body` 声明校验与元数据的方式一样，可以使用 Pydantic 的 `Field` 在 Pydantic 模型内部声明校验和元数据。

## 导入 `Field` { #import-field }

首先，从 Pydantic 中导入 `Field`：

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[4] *}

/// warning | 警告

注意，与从 `fastapi` 导入 `Query`，`Path`、`Body` 不同，要直接从 `pydantic` 导入 `Field` 。

///

## 声明模型属性 { #declare-model-attributes }

然后，使用 `Field` 定义模型的属性：

			expectedSync: true,
		},

		{ // 2. replication status Failed
			name: "existing object replication on object in Failed replication status",
			info: ObjectInfo{
				Size:                      100,
				ReplicationStatusInternal: "arn1:FAILED",
				ReplicationStatus:         replication.Failed,
				VersionID:                 "a3348c34-c352-4498-82f0-1098e8b34df9",
			},

    // Due to the implementation of the two services we know that both are now failed.  So the
    // following awaitHealthy call is just to get the exception.
    manager.startAsync();
    assertThat(manager.servicesByState().get(State.FAILED)).hasSize(2);
    IllegalStateException e = assertThrows(IllegalStateException.class, manager::awaitHealthy);
    assertThat(e)

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *

    }

    // Test field assignment
    @Test
    public void test_fieldAssignment() {
        String[] fields = new String[] { "field1", "field2", "field3" };
        facetInfo.field = fields;
        assertNotNull(facetInfo.field);
        assertEquals(3, facetInfo.field.length);
        assertSame(fields, facetInfo.field);
    }

    }

    /**
     * Adds a field and text pair to the field log for tracking query terms.
     * @param field The field name.
     * @param text The query text for this field.
     */
    public void addFieldLog(final String field, final String text) {
        if (fieldLogMap == null) {
            return;
        }

        List<String> list = fieldLogMap.get(field);
        if (list == null) {

## Import `Field` { #import-field }

First, you have to import it:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[4] *}


/// warning

Notice that `Field` is imported directly from `pydantic`, not from `fastapi` as are all the rest (`Query`, `Path`, `Body`, etc).

///

		},
		{
			name: "XIgnoreFoo does not have to appear in policy",
			fv:   defaultFormVals.Clone().Set("X-Ignore-Foo", "my-foo-value"),
		},
		{
			name: "File does not have to appear in policy",
			fv:   defaultFormVals.Clone().Set("File", "file-value"),
		},
		{
			name: "Signature does not have to appear in policy",
			fv:   defaultFormVals.Clone().Set(xhttp.AmzSignatureV2, "signature-value"),
		},
		{