Spring MVC Annotation Method Scan order for service and controller

Reprint: http://blog.csdn.net/xwnxwn/article/details/52679578

Ways to get Webapplicationcontext: http://panyongzheng.iteye.com/admin/blogs/1477702

XML is scanned in sequence reference: http://sence-qi.iteye.com/blog/1328902

The bean that @controller annotations can be successfully scanned in the following way, not the bean that the @service/@Repository is scanned. That's right

Java code

1. <context:component-scan base-package="Org.bdp.system.test.controller" >
2. <context:include-filter type="annotation" expression="Org.springframework.stereotype.Controller"/>
3. </context:component-scan>

But the following way, not only scanning @controller, but also scanning @service/@Repository beans, may cause some problems

Java code

1. <context:component-scan base-package="ORG.BDP" >
2. <context:include-filter type="annotation" expression="Org.springframework.stereotype.Controller"/>
3. </context:component-scan>

This is especially true in the case of integration with Springmvc+spring+hibernate, the most typical error is:

Transaction does not work

What's the problem?

Analysis

1, <context:component-scan> will be handed over to org.springframework.context.config.ContextNamespaceHandler processing;

Java code

1. Registerbeandefinitionparser ("Component-scan", new Componentscanbeandefinitionparser ());

2. Componentscanbeandefinitionparser will read the configuration file information and assemble it into org.springframework.context.annotation.ClassPathBeanDefinitionScanner for processing;

3. If there is no Use-default-filters property configured <context:component-scan>, the default is true, The following code is called when the Classpathbeandefinitionscanner is created, depending on whether Use-default-filters is true:

Java code

2. protected void Registerdefaultfilters () {
4. This.includeFilters.add (new Annotationtypefilter (Component.   Class));
6. ClassLoader cl = Classpathscanningcandidatecomponentprovider.  Class.getclassloader ();
8. try {
10. This.includeFilters.add (new Annotationtypefilter (
12. (CLASS<?  extends Annotation>) cl.loadclass ("Javax.annotation.ManagedBean"), false));
14. Logger.info ("JSR-250 ' Javax.annotation.ManagedBean ' found and supported for component scanning");
16. }
18. catch (ClassNotFoundException ex) {
20. //JSR-250 1.1 API (as included in Java EE 6) is not available-simply skip.
22. }
24. try {
26. This.includeFilters.add (new Annotationtypefilter (
28. (CLASS<?  extends Annotation>) cl.loadclass ("javax.inject.Named"), false));
30. Logger.info ("JSR-330 ' javax.inject.Named ' annotation found and supported for component scanning");
32. }
34. catch (ClassNotFoundException ex) {
36. //JSR-330 API not available-simply skip.
38. }

Both the @Service and @controller are component, because these annotations add @component annotations

You can see that the default Classpathbeandefinitionscanner automatically registers @component, @ManagedBean, @Named annotated beans for scanning. If we are careful, we will find the source of the problem.

4, in the scan will be include-filter/exclude-filter to determine whether your bean class is legitimate:

Java code

2. Protected Boolean iscandidatecomponent (Metadatareader metadatareader) throws IOException {
4. For (TypeFilter TF: this.excludefilters) {
6. if (Tf.match (Metadatareader, this.metadatareaderfactory)) {
8. return false;
10. }
12. }
14. For (TypeFilter TF: this.includefilters) {
16. if (Tf.match (Metadatareader, this.metadatareaderfactory)) {
18. Annotationmetadata metadata = Metadatareader.getannotationmetadata ();
20. if (!metadata.isannotated. Class.getname ())) {
22. return true;
24. }
26. Annotationattributes profile = metadatautils.attributesfor (metadata, profile.   Class);
28. return this.environment.acceptsProfiles (Profile.getstringarray ("value"));
30. }
32. }
34. return false;
36. }

The default scan specifies that all @Component under the package, Exclude-filter specifies that no scans, Include-filter specified scans, Include-filter, and Exclude-filter are still scanned that are not specified. To

Use-default-filters= "false" is specified.
First, the blacklist is filtered by exclude-filter;

Then through the Include-filter white list filter;

Otherwise, the default exclusion

Conclusion Java code

1. <context:component-scan base-package="ORG.BDP" >
2. <context:include-filter type="annotation" expression="Org.springframework.stereotype.Controller"/>
3. </context:component-scan>

Why this code not only scans @controller annotated beans, but also scans the @component sub-annotations @service, @Reposity. Because use-default-filters defaults to true. So if the default is not required, use-default-filters= "false" is disabled.

Spring MVC Annotation Method Scan order for service and controller