从JDK 1.5到1.6的代码迁移

Question

What are the steps to be followed for Migration of code from JDK 1.5 to 1.6.

Steps followed :

1. Changed the build Patch of Project as JDK1.6
2. Changed the Compiler as 6
3. Clean and deploy the Project
4. I was getting Compilation error as

*** ERROR ***: Thu Apr 01 05:17:06 PDT 2010    org.eclipse.jst.j2ee.commonarchivecore.internal.exception.DeploymentDescriptorLoadException: WEB-INF/web.xml
    Stack trace of nested exception:
    java.lang.ClassCastException: org.eclipse.jst.javaee.web.internal.impl.WebAppDeploymentDescriptorImpl cannot be cast to org.eclipse.jst.j2ee.webapplication.WebApp
        at org.eclipse.jst.j2ee.commonarchivecore.internal.strategy.War22ImportStrategyImpl.loadDeploymentDescriptor(War22ImportStrategyImpl.java:87)
        at org.eclipse.jst.j2ee.commonarchivecore.internal.strategy.War22ImportStrategyImpl.importMetaData(War22ImportStrategyImpl.java:81)
        at org.eclipse.jst.j2ee.commonarchivecore.internal.impl.WARFileImpl.getDeploymentDescriptor(WARFileImpl.java:145)  



*** ERROR ***: Thu Apr 01 05:17:06 PDT 2010    org.eclipse.wst.validation.internal.core.ValidationException: CHKJ3000E: WAR Validation Failed: org.eclipse.jst.j2ee.commonarchivecore.internal.exception.DeploymentDescriptorLoadException: WEB-INF/web.xml
        at org.eclipse.jst.j2ee.model.internal.validation.WarValidator.validateInJob(WarValidator.java:343)
        at org.eclipse.jst.j2ee.internal.web.validation.UIWarValidator.validateInJob(UIWarValidator.java:111)
        at org.eclipse.wst.validation.internal.operations.ValidatorJob.run(ValidatorJob.java:75)
        at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

Answer 1

In the vast majority of cases, you don't need to do anything at all. Even recompiling is not strictly necessary.

The few incompatibilities that exist between Java 5.0 and 6.0 are documented in the JDK 6 Adoption Guide .

Answer 2

The code that ran on Java 1.5 will run on 1.6 without any modifications(in you weren't using any internal APIs that is). The public Java api is always forward compatible.

Answer 3

使用新的JDK重新编译，检查警告（可能不推荐使用某些类或方法），检查应用程序是否按预期工作。

Answer 4

I did following and it works fine

Changed the build Patch of Project as JDK1.6
Changed the Compiler as 6 

Answer 5

Download and install JDK 6. Update any environmental variables like JAVA_HOME, JDK_HOME. Make sure that your IDE points to the new library (most IDEs will do it automatically if restarted after the environmental variables have been updated). Update the project settings to use JDK 6 in your IDE for each project respectively.

Answer 6

That depends on your application I suppose here are the list of new features to 1.6 all your code however should work fine.

link java 1.6 features

Answer 7

I fixed a similar error by replacing:

<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
     version="2.4">

with:

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
     version="3.1">

When I did this replacement at web.xml, this CHKJ3000E has gone away.