聊聊CanalInstanceGenerator

序

本文主要研究一下CanalInstanceGenerator

CanalInstanceGenerator

canal-1.1.4/instance/core/src/main/java/com/alibaba/otter/canal/instance/core/CanalInstanceGenerator.java

<code>
public
 
interface
 
CanalInstanceGenerator
 
{
​
     
    
CanalInstance 
generate
(String destination)
;
}/<code>

• CanalInstanceGenerator定義了generate方法用於創建指定destination的CanalInstance

PlainCanalInstanceGenerator

canal-1.1.4/instance/manager/src/main/java/com/alibaba/otter/canal/instance/manager/PlainCanalInstanceGenerator.java

<code>
public
 
class
 
PlainCanalInstanceGenerator
 
implements
 
CanalInstanceGenerator
 
{
​
    
private
 
static
 
final
 Logger    logger      = LoggerFactory.getLogger(SpringCanalInstanceGenerator
.
class
)
;
    
private
 String                 springXml;
    
private
 PlainCanalConfigClient canalConfigClient;
    
private
 String                 defaultName = 
"instance"
;
    
private
 BeanFactory            beanFactory;
    
private
 Properties             canalConfig;
​
    
public
 
PlainCanalInstanceGenerator
(Properties canalConfig)
{
        
this
.canalConfig = canalConfig;
    }
​
    
public
 CanalInstance 
generate
(String destination)
 
{
        
synchronized
 (CanalInstanceGenerator
.
class
) 
{
            
try
 {
                PlainCanal canal = canalConfigClient.findInstance(destination, 
null
);
                
if
 (canal == 
null
) {
                    
throw
 
new
 CanalException(
"instance : "
 + destination + 
" config is not found"
);
                }
                Properties properties = canal.getProperties();
                 
                properties.putAll(canalConfig);
​
                 
                com.alibaba.otter.canal.instance.spring.support.PropertyPlaceholderConfigurer.propertiesLocal.set(properties);
                 
                System.setProperty(
"canal.instance.destination"
, destination);
                
this
.beanFactory = getBeanFactory(springXml);
                String beanName = destination;
                
if
 (!beanFactory.containsBean(beanName)) {
                    beanName = defaultName;
                }
​
                
return
 (CanalInstance) beanFactory.getBean(beanName);
            } 
catch
 (Throwable e) {
                logger.error(
"generator instance failed."
, e);
                
throw
 
new
 CanalException(e);
            } 
finally
 {
                System.setProperty(
"canal.instance.destination"
, 
""
);
            }
        }
    }
​
     
​
    
private
 BeanFactory 
getBeanFactory
(String springXml)
 
{
        ApplicationContext applicationContext = 
new
 ClassPathXmlApplicationContext(springXml);
        
return
 applicationContext;
    }
​
    
public
 
void
 
setCanalConfigClient
(PlainCanalConfigClient canalConfigClient)
 
{
        
this
.canalConfigClient = canalConfigClient;
    }
​
    
public
 
void
 
setSpringXml
(String springXml)
 
{
        
this
.springXml = springXml;
    }
​
}/<code>

• PlainCanalInstanceGenerator實現了CanalInstanceGenerator接口，其generate方法通過canal.getProperties()設置相關屬性，然後再通過beanFactory.getBean(beanName)獲取CanalInstance

ManagerCanalInstanceGenerator

canal-1.1.4/instance/manager/src/main/java/com/alibaba/otter/canal/instance/manager/ManagerCanalInstanceGenerator.java

<code>
public
 
class
 
ManagerCanalInstanceGenerator
 
implements
 
CanalInstanceGenerator
 
{
​
    
private
 CanalConfigClient canalConfigClient;
​
    
public
 CanalInstance 
generate
(String destination)
 
{
        Canal canal = canalConfigClient.findCanal(destination);
        String filter = canalConfigClient.findFilter(destination);
        
return
 
new
 CanalInstanceWithManager(canal, filter);
    }
​
     
​
    
public
 
void
 
setCanalConfigClient
(CanalConfigClient canalConfigClient)
 
{
        
this
.canalConfigClient = canalConfigClient;
    }
​
}/<code>

• ManagerCanalInstanceGenerator實現了CanalInstanceGenerator接口，其generate方法通過canalConfigClient獲取canal及filter，然後創建CanalInstanceWithManager

SpringCanalInstanceGenerator

canal-1.1.4/instance/spring/src/main/java/com/alibaba/otter/canal/instance/spring/SpringCanalInstanceGenerator.java

<code>
public
 
class
 
SpringCanalInstanceGenerator
 
implements
 
CanalInstanceGenerator
 
{
​
    
private
 
static
 
final
 Logger logger      = LoggerFactory.getLogger(SpringCanalInstanceGenerator
.
class
)
;
    
private
 String              springXml;
    
private
 String              defaultName = 
"instance"
;
    
private
 BeanFactory         beanFactory;
​
    
public
 CanalInstance 
generate
(String destination)
 
{
        
synchronized
 (CanalInstanceGenerator
.
class
) 
{
            
try
 {
                 
                System.setProperty(
"canal.instance.destination"
, destination);
                
this
.beanFactory = getBeanFactory(springXml);
                String beanName = destination;
                
if
 (!beanFactory.containsBean(beanName)) {
                    beanName = defaultName;
                }
​
                
return
 (CanalInstance) beanFactory.getBean(beanName);
            } 
catch
 (Throwable e) {
                logger.error(
"generator instance failed."
, e);
                
throw
 
new
 CanalException(e);
            } 
finally
 {
                System.setProperty(
"canal.instance.destination"
, 
""
);
            }
        }
    }
​
    
private
 BeanFactory 
getBeanFactory
(String springXml)
 
{
        ApplicationContext applicationContext = 
new
 ClassPathXmlApplicationContext(springXml);
        
return
 applicationContext;
    }
​
    
public
 
void
 
setSpringXml
(String springXml)
 
{
        
this
.springXml = springXml;
    }
}/<code>

• SpringCanalInstanceGenerator實現了CanalInstanceGenerator接口，其generate方法通過beanFactory.getBean(beanName)獲取CanalInstance

小結

CanalInstanceGenerator定義了generate方法用於創建指定destination的CanalInstance；它有三個實現類分別是PlainCanalInstanceGenerator、ManagerCanalInstanceGenerator、SpringCanalInstanceGenerator

doc

• CanalInstanceGenerator