在bean初始化期间如何调用数据源? [英] How to call datasource during bean initialization?
问题描述
我有一个托管bean，它从数据库表中获取设置和值的列表.
I have a managed bean which gets list of settings and values from database table.
import java.io.Serializable;
import javax.enterprise.context.SessionScoped;
// or import javax.faces.bean.SessionScoped;
import javax.inject.Named;
/* include SQL Packages */
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import javax.sql.DataSource;
import javax.annotation.Resource;
import javax.faces.context.FacesContext;
import javax.inject.Inject;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
// or import javax.faces.bean.ManagedBean;
import org.glassfish.osgicdi.OSGiService;
@Named("DashboardController")
@SessionScoped
public class Dashboard implements Serializable {
private String SessionTTL = null;
private String MaxActiveUsers = null;
private String SQL_Statement = null;
private HashMap<String, String> settingsMap = null;
public Dashboard() throws SQLException
{
initSettings();
/*try { initSettings(); }
catch (SQLException ex) { ex.printStackTrace(); }
*
*/
}
/* Call the Oracle JDBC Connection driver */
@Resource(name = "jdbc/Oracle")
private DataSource ds;
public String settingValue(String key)
{
try
{
return (String) settingsMap.get(key);
}
catch(Exception x) { return "error - " + x.getMessage(); }
}
public void initSettings() throws SQLException
{
settingsMap = new HashMap<String, String>();
if(ds == null) {
throw new SQLException("Can't get data source");
}
Connection conn = ds.getConnection();
if(conn == null) {
throw new SQLException("Can't get database connection");
}
PreparedStatement ps = conn.prepareStatement("SELECT * from GLOBALSETTINGS");
try
{
//get data from database
ResultSet result = ps.executeQuery();
while (result.next())
{
settingsMap.put(result.getString("SettingName"), result.getString("SettingValue"));
}
}
finally
{
ps.close();
conn.close();
}
}
}
当我运行代码时，我在Glassfish中得到了这个错误堆栈
When I run the code I get this error stack in Glassfish
com.sun.faces.mgbean.ManagedBeanCreationException: Cant instantiate class: com.DX_57.SM_57.Dashboard.
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:193)
at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:102)
at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:409)
at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:269)
at com.sun.faces.el.ManagedBeanELResolver.resolveBean(ManagedBeanELResolver.java:244)
at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:116)
at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
at com.sun.el.parser.AstIdentifier.getValue(AstIdentifier.java:103)
at com.sun.el.parser.AstValue.getValue(AstValue.java:179)
at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:224)
at com.sun.faces.facelets.el.ELText$ELTextVariable.writeText(ELText.java:227)
at com.sun.faces.facelets.compiler.TextInstruction.write(TextInstruction.java:85)
at com.sun.faces.facelets.compiler.UIInstructions.encodeBegin(UIInstructions.java:82)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:302)
at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:105)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:304)
at com.sun.faces.renderkit.html_basic.GridRenderer.renderRow(GridRenderer.java:185)
at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:129)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1757)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:402)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1542)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:849)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:746)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1045)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:228)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.sql.SQLException: Can't get data source
at com.DX_57.SM_57.Dashboard.initSettings(Dashboard.java:162)
at com.DX_57.SM_57.Dashboard.<init>(Dashboard.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at java.lang.Class.newInstance0(Class.java:372)
at java.lang.Class.newInstance(Class.java:325)
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:188)
... 52 more
我正在尝试在bean构造函数中初始化一个哈希表，然后调用 jsf页面中的settingValue方法传递一个字符串参数.
I'm trying to initialize a hashmap in the bean constructor and then call settingValue method in jsf page passing a string parameter.
<h:panelGroup>Key</h:panelGroup>
<h:panelGroup>#{DashboardController.settingValue(SessionTTL)}
</h:panelGroup>
是否有可能在调用bean的构造函数之前初始化数据源. 在bean初始化之后如何立即进行SQL查询.
Is it possible to initialize the data source prior invoking bean's constructor. How I can make SQL queries right after bean initialization.
推荐答案
是否可以在调用bean的构造函数之前初始化数据源.在bean初始化后如何立即进行SQL查询.
那是不可能的.只能在构造实例后 注入依赖项资源.在没有具体实例的情况下，根本没有什么可以注入资源的.
That's not possible. The dependency resources can only be injected after construction of the instance. Without having a concrete instance, there's simply nothing where the resources can be injected in.
要在依赖项注入后立即执行操作，发明了@PostConstruct批注.您需要使用它而不是构造函数.
To perform actions directly after dependency injection, the @PostConstruct annotation is been invented. You need to use it instead of the constructor.
替换
public Dashboard() throws SQLException {
initSettings();
}
public void initSettings() throws SQLException {
// ...
}
作者
@PostConstruct
public void initSettings() throws SQLException {
// ...
}
在依赖项注入之后，直接调用以@PostConstruct注释的方法，如@Resource，@Inject，@EJB，@ManagedProperty等所执行的.
A method annotated with @PostConstruct is invoked directly after dependency injection as is been performed by @Resource, @Inject, @EJB, @ManagedProperty, etc.
不相关与具体问题无关，使用附加方法访问地图值的方式不必要地过于复杂.只需使用一个简单的吸气剂
Unrelated to the concrete problem, the way how you access a map value with an additional method is unnecessarily overcomplicated. Just have a simple getter for it
public Map<String, String> getSettings() {
return settingsMap;
}
并按以下方式访问地图值:
and access the map values as follows:
#{DashboardController.settings['SessionTTL']}
或地图键不包含句点时:
or when the map key doesn't contain periods:
#{DashboardController.settings.SessionTTL}
另请参见:
- 我们的EL Wiki页面
- Our EL wiki page
See also:
顺便说一句，实例名称以大写字母(例如#{DashboardController})而不是小写字母(例如#{dashboardController}(或者只是默认的#{dashboard}))开头也是一种较差的编码约定.
By the way, starting instance names with an uppercase like #{DashboardController} instead of lowercase like #{dashboardController} (or just the default #{dashboard}) is also a poor coding convention.
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