问题描述
这可能是一个非常新手的问题,但我已经搜索过,要么我的理解存在很大的差距,要么我做错了,我无法弄清楚。
this may be a very novice question, but I have searched and either I have a large gap in my understanding or am doing something incorrectly that I cannot figure out.
在我的上下文文件中这里是摘录
In my context file here is an excerpt
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="${datasource.driverClassName}" />
<property name="url" value="${datasource.url}" />
<property name="username" value="${datasource.username}" />
<property name="password" value="${datasource.password}" />
</bean>
<bean id="myBeanOne" class="a.b.c.myBeanOne">
<property name="dataSource" ref="dataSource" />
</bean>
现在在myBeanOne中我有:
Now in myBeanOne I have:
private DataSource dataSource;
private JdbcTemplate jdbcTemplate;
@Autowired
public void setDataSource (DataSource dataSource) {
this.jdbcTemplate = new JdbcTemplate(dataSource);
}
public void myMethod() {
String sql = "'My generic SQL update query'";
try {
this.jdbcTemplate.update(sql);
} catch (org.springframework.dao.EmptyResultDataAccessException ex) {
}
System.exit(0);
}
当我尝试在调用setDataSource的行上执行此操作时我得到了这个错误:
when I try to execute this on the line where setDataSource is invoked I get this error:
ERROR org.springframework.integration.handler.LoggingHandler
org.springframework.integration.MessageHandlingException:
java.lang.NullPointerException
: this.jdbcTemplate。更新(sql);
我尝试了十种不同的配置来实现这一点,但我似乎无法做到。感谢您的任何帮助。
I have tried maybe ten different configurations to get this to work, but I cannot seem to do it. Any assistance is appreciated, thank you.
编辑:根据Luiggi的评论:
as per Luiggi's comment:
//in yet another classes run method
myBeanOne bOne = SomeOtherClass.create(); //just returns new myBeanOne
bOne.myMethod();
SomeOtherClass或此类在上下文中都不归类为bean或在上下文中有任何存在。
Neither SomeOtherClass or this class are classified as beans in the context or have any presence in the context.
我知道这是一个非常基本的问题,但我正在努力解决这个问题。
I know that this is a very basic question but I am struggling with it.
感谢您的耐心等待。
推荐答案
如评论中所述,问题在于您手动创建bean而不是让Spring容器创建它。基本上,你这样做:
As noted in comments, the problem is that you're manually creating the bean instead of letting Spring container create it. Basically, you're doing this:
new MyBeanOne()
因此,Spring容器无法注入您配置的任何字段,因此 null
例如 jdbcTemplate
字段。有一些解决方案:
So Spring container can't inject any of the fields you have configured thus being null
e.g. jdbcTemplate
field. There are some solutions to this:
-
将
SomeOtherClass
转换为由Spring容器管理的bean,让它注入MyBeanOne
实例(可能使用@Autowired
注释)。
Convert your
SomeOtherClass
into a bean managed by Spring container and let it inject theMyBeanOne
instance (probably using@Autowired
annotation).
如果由于您需要手动创建bean而无法完成后一种方法,您可以手动创建bean,如下所示:
If latter approach can't be done since you need to manually create the bean, you can create the bean manually as shown here: How to create spring beans dynamically?
但是这个实现使你硬编码弹簧配置文件名并在你的代码中使用它。因此,更好的方法是选项3.
But this implementation makes you hardcode somewhere the spring config file name and use it in your code. So, a better approach would be option 3.
看看这个解决方案:
- Spring Framework: 7.8 Using AspectJ with Spring applications
- Using Spring's @Configurable in three easy steps
请注意,要启用此功能,您必须添加启动JVM时的java代理,它将在运行时使用方面编写类。
Note that in order to enable this feature, you have to add a java agent when starting the JVM that will weave the class at runtime using aspects.
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