1、簡(jiǎn)述
如何使用SnakeYAML庫(kù)將
YAML文檔轉(zhuǎn)換為Java對(duì)象，以及JAVA對(duì)象如何序列化為YAML文檔。
在DevOps平臺(tái)系統(tǒng)中是基礎(chǔ)的能力支持，不管是spring boot 的配置還是K8S 資源清單yaml
2、項(xiàng)目設(shè)置
要在項(xiàng)目中使用SnakeYAML，需要添加Maven依賴項(xiàng)（可在此處找到最新版本）
<dependency>
<groupId>org.yaml</groupId>
<artifactId>snakeyaml</artifactId>
<version>1.25</version>
</dependency>3、入口點(diǎn)
該YAML類是API的入口點(diǎn)：
Yaml yaml = new Yaml()由于實(shí)現(xiàn)不是線程安全的，因此不同的線程必須具有自己的Yaml實(shí)例。
4、加載YAML文檔
SnakeYAML支持從String或InputStream加載文檔，我們從定義一個(gè)簡(jiǎn)單的YAML文檔開(kāi)始，然后將文件命名為customer.yaml：
基本用法
現(xiàn)在，我們將使用Yaml類來(lái)解析上述YAML文檔：
public class YamlTest {
public static void main(String[] args) {
Yaml yaml = new Yaml();
InputStream inputStream = YamlTest.class
.getClassLoader()
.getResourceAsStream("customer.yaml");
Map<String, Object> obj = yaml.load(inputStream);
System.out.println(obj);
}
}上面的代碼生成以下輸出：?
?文章來(lái)源：http://www.zghlxwxcb.cn/news/detail-536040.html
默認(rèn)情況下，load（）方法返回一個(gè)Map對(duì)象。查詢Map對(duì)象時(shí)，我們需要事先知道屬性鍵的名稱，否則容易出錯(cuò)。更好的辦法是自定義類型。
自定義類型解析
SnakeYAML提供了一種將文檔解析為自定義類型的方法
讓我們定義一個(gè)Customer類，然后嘗試再次加載該文檔：
package com.devops.autocicdstore.yaml;
/**
* @Author 虎哥
* @Description //TODO
* |要帶著問(wèn)題去學(xué)習(xí),多猜想多驗(yàn)證|
**/
public class Customer {
private String firstName;
private String lastName;
private int age;
// getters and setters
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Customer{" +
"firstName='" + firstName + '\'' +
", lastName='" + lastName + '\'' +
", age=" + age +
'}';
}
}
現(xiàn)在我么來(lái)加載：?
Yaml yaml = new Yaml(new Constructor(Customer.class));
InputStream inputStream = YamlTest.class
.getClassLoader()
.getResourceAsStream("customer.yaml");
Customer customer = yaml.load(inputStream);
System.out.println(customer);隱式類型
如果沒(méi)有為給定屬性定義類型，則庫(kù)會(huì)自動(dòng)將值轉(zhuǎn)換為隱式type。
例如：
1.0 -> Float
42 -> Integer
2009-03-30 -> Date讓我們使用一個(gè)TestCase來(lái)測(cè)試這種隱式類型轉(zhuǎn)換：
@org.junit.Test
public void whenLoadYAML_thenLoadCorrectImplicitTypes() {
Yaml yaml = new Yaml();
Map<Object, Object> document = yaml.load("3.0: 2018-07-22");
System.out.println(document);
assertNotNull(document);
assertEquals(1, document.size());
assertTrue(document.containsKey(3.0d));
}嵌套對(duì)象
SnakeYAML?支持嵌套的復(fù)雜類型。
讓我們向“?customer.yaml”添加“?聯(lián)系方式”??和“?地址”?詳細(xì)信息，并將新文件另存為customer_with_contact_details_and_address.yaml.。
現(xiàn)在，我們將分析新的YAML文檔
firstName: "John"
lastName: "Doe"
age: 31
contactDetails:
- type: "mobile"
number: 123456789
- type: "landline"
number: 456786868
homeAddress:
line: "Xyz, DEF Street"
city: "City Y"
state: "State Y"
zip: 345657我們來(lái)更新java類：
package com.devops.autocicdstore.yaml;
import java.util.List;
/**
* @Author 虎哥
* @Description //TODO
* |要帶著問(wèn)題去學(xué)習(xí),多猜想多驗(yàn)證|
**/
public class Customer {
private String firstName;
private String lastName;
private int age;
private List<Contact> contactDetails;
private Address homeAddress;
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public List<Contact> getContactDetails() {
return contactDetails;
}
public void setContactDetails(List<Contact> contactDetails) {
this.contactDetails = contactDetails;
}
public Address getHomeAddress() {
return homeAddress;
}
public void setHomeAddress(Address homeAddress) {
this.homeAddress = homeAddress;
}
@Override
public String toString() {
return "Customer{" +
"firstName='" + firstName + '\'' +
", lastName='" + lastName + '\'' +
", age=" + age +
", contactDetails=" + contactDetails +
", homeAddress=" + homeAddress +
'}';
}
}
package com.devops.autocicdstore.yaml;
/**
* @Author 虎哥
* @Description //TODO
* |要帶著問(wèn)題去學(xué)習(xí),多猜想多驗(yàn)證|
**/
public class Address {
private String line;
private String city;
private String state;
private Integer zip;
public String getLine() {
return line;
}
public void setLine(String line) {
this.line = line;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public Integer getZip() {
return zip;
}
public void setZip(Integer zip) {
this.zip = zip;
}
@Override
public String toString() {
return "Address{" +
"line='" + line + '\'' +
", city='" + city + '\'' +
", state='" + state + '\'' +
", zip=" + zip +
'}';
}
}
package com.devops.autocicdstore.yaml;
/**
* @Author 虎哥
* @Description //TODO
* |要帶著問(wèn)題去學(xué)習(xí),多猜想多驗(yàn)證|
**/
public class Contact {
private String type;
private int number;
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public int getNumber() {
return number;
}
public void setNumber(int number) {
this.number = number;
}
@Override
public String toString() {
return "Contact{" +
"type='" + type + '\'' +
", number=" + number +
'}';
}
}
現(xiàn)在，我們來(lái)測(cè)試下Yaml＃load（）：
@Test
public void
whenLoadYAMLDocumentWithTopLevelClass_thenLoadCorrectJavaObjectWithNestedObjects() {
Yaml yaml = new Yaml(new Constructor(Customer.class));
InputStream inputStream = this.getClass()
.getClassLoader()
.getResourceAsStream("customer_with_contact_details_and_address.yaml");
Customer customer = yaml.load(inputStream);
System.out.println(customer);
assertNotNull(customer);
assertEquals("John", customer.getFirstName());
assertEquals("Doe", customer.getLastName());
assertEquals(31, customer.getAge());
assertNotNull(customer.getContactDetails());
assertEquals(2, customer.getContactDetails().size());
assertEquals("mobile", customer.getContactDetails()
.get(0)
.getType());
assertEquals(123456789, customer.getContactDetails()
.get(0)
.getNumber());
assertEquals("landline", customer.getContactDetails()
.get(1)
.getType());
assertEquals(456786868, customer.getContactDetails()
.get(1)
.getNumber());
assertNotNull(customer.getHomeAddress());
assertEquals("Xyz, DEF Street", customer.getHomeAddress()
.getLine());
}
?
類型安全的集合
當(dāng)給定Java類的一個(gè)或多個(gè)屬性是泛型集合類時(shí)，需要通過(guò)TypeDescription來(lái)指定泛型類型，以便可以正確解析。
讓我們假設(shè)?一個(gè)Customer擁有多個(gè)Contact：
firstName: "John"
lastName: "Doe"
age: 31
contactDetails:
- { type: "mobile", number: 123456789}
- { type: "landline", number: 123456789}為了能正確解析，我們可以在頂級(jí)類上為給定屬性指定TypeDescription?：
@Test
public void test1(){
Constructor constructor = new Constructor(Customer.class);
TypeDescription customTypeDescription = new TypeDescription(Customer.class);
customTypeDescription.addPropertyParameters("contactDetails", Contact.class);
constructor.addTypeDescription(customTypeDescription);
Yaml yaml = new Yaml(new Constructor(Customer.class));
InputStream inputStream = this.getClass()
.getClassLoader()
.getResourceAsStream("customer_with_contact_details_and_address.yaml");
Customer customer = yaml.load(inputStream);
System.out.println(customer);
}
?
?
載入多個(gè)文件
在某些情況下，單個(gè)文件中可能有多個(gè)YAML文檔，而我們想解析所有文檔。所述YAML類提供了一個(gè)LOADALL（）方法來(lái)完成這種類型的解析。
假設(shè)下面的內(nèi)容在一個(gè)文件中：
---
firstName: "John"
lastName: "Doe"
age: 20
---
firstName: "Jack"
lastName: "Jones"
age: 25我們可以使用loadAll（）方法解析以上內(nèi)容，如以下代碼示例所示：
@Test
public void whenLoadMultipleYAMLDocuments_thenLoadCorrectJavaObjects() {
Yaml yaml = new Yaml(new Constructor(Customer.class));
InputStream inputStream = this.getClass()
.getClassLoader()
.getResourceAsStream("customers.yaml");
int count = 0;
for (Object object : yaml.loadAll(inputStream)) {
count++;
assertTrue(object instanceof Customer);
System.out.println(object);
}
assertEquals(2,count);
}
5、生成YAML文件
SnakeYAML?支持 將java對(duì)象序列化為yml。
基本用法
我們將從一個(gè)將Map <String，Object>的實(shí)例轉(zhuǎn)儲(chǔ)到Y(jié)AML文檔（String）的簡(jiǎn)單示例開(kāi)始：
@Test
public void whenDumpMap_thenGenerateCorrectYAML() {
Map<String, Object> data = new LinkedHashMap<String, Object>();
data.put("name", "Silenthand Olleander");
data.put("race", "Human");
data.put("traits", new String[] { "ONE_HAND", "ONE_EYE" });
Yaml yaml = new Yaml();
StringWriter writer = new StringWriter();
yaml.dump(data, writer);
String expectedYaml = "name: Silenthand Olleander\nrace: Human\ntraits: [ONE_HAND, ONE_EYE]\n";
System.out.println(writer);
assertEquals(expectedYaml, writer.toString());
}上面的代碼產(chǎn)生以下輸出（請(qǐng)注意，使用LinkedHashMap的實(shí)例將保留輸出數(shù)據(jù)的順序）：
自定義Java對(duì)象
我們還可以選擇將自定義Java類型轉(zhuǎn)儲(chǔ)到輸出流中。
@Test
public void whenDumpACustomType_thenGenerateCorrectYAML() {
Customer customer = new Customer();
customer.setAge(45);
customer.setFirstName("Greg");
customer.setLastName("McDowell");
Yaml yaml = new Yaml();
StringWriter writer = new StringWriter();
yaml.dump(customer, writer);
String expectedYaml = "!!com.devops.autocicdstore.yaml.Customer {age: 45, contactDetails: null, firstName: Greg,\n homeAddress: null, lastName: McDowell}\n";
System.out.println(writer);
assertEquals(expectedYaml, writer.toString());
}?
?
?
生成內(nèi)容會(huì)包含!!com.devops.autocicdstore.yaml.Customer，為了避免在輸出文件中使用標(biāo)簽名，我們可以使用庫(kù)提供的??dumpAs（）方法。
因此，在上面的代碼中，我們可以進(jìn)行以下調(diào)整以刪除標(biāo)記：
yaml.dumpAs(customer, Tag.MAP, null);String ccustomerStr = yaml.dumpAs(customer, Tag.MAP, null);
System.out.println(ccustomerStr);
?
?
?本文說(shuō)明了SnakeYAML庫(kù)解析和序列化YAML文檔。文章來(lái)源地址http://www.zghlxwxcb.cn/news/detail-536040.html
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