Spring教程 - 彈簧依賴檢查

Spring教程 - 彈簧依賴檢查

Spring可以做依賴檢查以確保已設(shè)置或注入所需的屬性。

Spring可以做依賴檢查以確保已設(shè)置或注入所需的屬性。...

• none - No dependency checking. Default mode.
• simple - If any properties of primitive type (int, long, double...) and collection types (map, list...) have not been set, Spring throws UnsatisfiedDependencyException.
• objects - If any properties of object type have not been set, Spring will throw UnsatisfiedDependencyException.
• all - If any properties of any type have not been set, Spring will throw an UnsatisfiedDependencyException.

Java Bean

以下部分使用兩個(gè)Java bean如下所示以顯示如何使用依賴性檢查。

客戶類。

package com.www.o2fo.common;

public class Customer {
  private Person person;
  private int type;
  private String action;

  public Person getPerson() {
    return person;
  }

  public void setPerson(Person person) {
    this.person = person;
  }

  public int getType() {
    return type;
  }

  public void setType(int type) {
    this.type = type;
  }

  public String getAction() {
    return action;
  }

  public void setAction(String action) {
    this.action = action;
  }

  @Override
  public String toString() {
    return "Customer [person=" + person + ", type=" + type + ", action="
        + action + "]";
  }
}

人員類

package com.www.o2fo.common;

public class Person 
{
    private String name;
    private String address;
    private int age;
    public String getName() {
      return name;
    }
    public void setName(String name) {
      this.name = name;
    }
    public String getAddress() {
      return address;
    }
    public void setAddress(String address) {
      this.address = address;
    }
    public int getAge() {
      return age;
    }
    public void setAge(int age) {
      this.age = age;
    }
  @Override
  public String toString() {
    return "Person [name=" + name + ", address=" + address + ", age=" + age
        + "]";
  }
    
}

依賴性檢查:無

下面的代碼顯示了如何使用spring bean配置文件與“無"依賴性檢查模式。

<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
  http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
  <bean id="myCustomer" class="com.www.o2fo.common.Customer" >
    <property name="action" value="buy" />
  </bean>
  <bean id="myPerson" class="com.www.o2fo.common.Person">
    <property name="name" value="java2s" />
    <property name="address" value="address ABC" />
    <property name="age" value="29" />
  </bean>
</beans>

依賴關(guān)系檢查的默認(rèn)值為none。如果沒有明確定義依賴性檢查模式，它的默認(rèn)值為“none"，因此不會執(zhí)行依賴性檢查。

依賴性檢查:無...

依賴關(guān)系檢查的默認(rèn)值為none。如果沒有明確定義依賴性檢查模式，它的默認(rèn)值為“none"，因此不會執(zhí)行依賴性檢查。...

  <bean id="myCustomer" class="com.www.o2fo.common.Customer" 
         dependency-check="simple">

完整配置文件。

<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
  http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
  <bean id="myCustomer" class="com.www.o2fo.common.Customer" 
         dependency-check="simple">
    <property name="person" ref="myPerson" />
    <property name="action" value="buy" />
  </bean>
  <bean id="myPerson" class="com.www.o2fo.common.Person">
    <property name="name" value="java2s" />
    <property name="address" value="address ABC" />
    <property name="age" value="29" />
  </bean>
</beans>

完整配置文件。...

“type"屬性是類型int，它是一個(gè)基本類型尚未設(shè)置，一個(gè)UnsatisfiedDependencyException將拋出如下。

使用@Required注釋進(jìn)行Spring依賴性檢查

在下面我們將介紹另一種進(jìn)行依賴性檢查的方法。

我們可以使用@Required Annotation為Java bean添加依賴性檢查。

@Required注釋可應(yīng)用于特定屬性。

以下Customer對象在setPerson()方法中具有@Required以確保person屬性已設(shè)置。

package com.www.o2fo.common;
import org.springframework.beans.factory.annotation.Required;
public class Customer 
{
  private Person person;
  private int type;
  private String action;
  public Person getPerson() {
    return person;
  }
  @Required
  public void setPerson(Person person) {
    this.person = person;
  }
  public int getType() {
    return type;
  }
  public void setType(int type) {
    this.type = type;
  }
  public String getAction() {
    return action;
  }
  public void setAction(String action) {
    this.action = action;
  }
  
}

在對方法應(yīng)用@Required注釋之后，我們還需要注冊一個(gè)RequiredAnnotationBeanPostProcessor以確認(rèn)bean配置文件中的@Required注釋。

有兩種方法可以啟用RequiredAnnotationBeanPostProcessor。

• Add Spring context and <context:annotation-config /> in bean configuration file.
• Include "RequiredAnnotationBeanPostProcessor" directly in bean configuration file.

這里是上下文的語法:annotation-config。

<context:annotation-config />

完整的源代碼，

<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:context="http://www.springframework.org/schema/context"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
  http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
  http://www.springframework.org/schema/context
  http://www.springframework.org/schema/context/spring-context-2.5.xsd">

  <context:annotation-config />

  <bean id="CustomerBean" class="com.www.o2fo.common.Customer">
    <property name="action" value="buy" />
    <property name="type" value="1" />
  </bean>
  <bean id="PersonBean" class="com.www.o2fo.common.Person">
    <property name="name" value="java2s" />
    <property name="address" value="address ABC" />
    <property name="age" value="29" />
  </bean>
</beans>

以下xml代碼顯示如何包含“RequiredAnnotationBeanPostProcessor"在bean配置文件中。

<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
  http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
    <bean 
        class="org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor"/>
  <bean id="CustomerBean" class="com.www.o2fo.common.Customer">
    <property name="action" value="buy" />
    <property name="type" value="1" />
  </bean>
  <bean id="PersonBean" class="com.www.o2fo.common.Person">
    <property name="name" value="java2s" />
    <property name="address" value="address ABC" />
    <property name="age" value="29" />
  </bean>
</beans>

如果我們運(yùn)行它，將拋出以下錯(cuò)誤消息，因?yàn)槲丛O(shè)置person屬性。

org.springframework.beans.factory.BeanInitializationException: 
  Property "person" is required for bean "CustomerBean"

使用@Required注釋進(jìn)行Spring依賴性檢查...

我們可以定義自定義注釋，通過使用Spring進(jìn)行依賴性檢查@必需樣式注釋。

在下面的示例中，我們將創(chuàng)建一個(gè)名為@Mandatory的自定義@必需類型的注釋，這相當(dāng)于@Required注釋。

在下面的示例中，我們將創(chuàng)建一個(gè)名為@Mandatory的自定義@必需類型的注釋，這相當(dāng)于@Required注釋。...

package com.www.o2fo.common;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Mandatory {
}

然后，我們將新創(chuàng)建的注釋應(yīng)用于來自Java Bean的屬性。

package com.www.o2fo.common;

public class Customer 
{
  private Person person;
  private int type;
  private String action;

  @Mandatory
  public void setPerson(Person person) {
    this.person = person;
  }
}

最后，我們需要在xml配置文件中注冊它包括@Mandatory注釋在“RequiredAnnotationBeanPostProcessor"類中。

<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
  http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
    <bean class="org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor">
      <property name="requiredAnnotationType" value="com.www.o2fo.common.Mandatory"/>
    </bean>
  <bean id="CustomerBean" class="com.www.o2fo.common.Customer">
    <property name="action" value="buy" />
    <property name="type" value="1" />
  </bean>
</beans>