java - Spring ClassPathXmlApplicationContext 数据连接

Question

我正在尝试使用 Spring 3.2.0 创建连接，但出现 NullPointerException:

ApplicationContext ctx = new ClassPathXmlApplicationContext("conexao/conexao.xml")

我的文件 conexao.xml 位于 conexao 包中。我的 xml 文件配置如下:

<beans>
    <bean id="banco" class="modelo.Banco">
        <property name="usuario">
            <value>root</value>
        </property>
        <property name="senha">
            <value>""</value>
        </property>
        <property name="url">
            <value>jdbc:mysql://localhost:3306/agenda</value>
        </property>
        <property name="classForName">
            <value>com.mysql.jdbc.Driver</value>
        </property>
    </bean>
</beans>

它总是停在这样的地方，就像调试时一样:

ApplicationContext ctx = new ClassPathXmlApplicationContext("conexao/conexao.xml")

我的代码:

package dao;

import com.mysql.jdbc.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
import model.Banco;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Conexao {

    private static Banco banco;

    private static Conexao instance;

    public static Conexao getInstance() {
        if (Conexao.instance == null) {
            Conexao.instance = new Conexao();
        }
        return Conexao.instance;

    }

    private Conexao() {

    }

    public Connection abrirConexao() {
        ApplicationContext ctx = new ClassPathXmlApplicationContext(
                "conexao/conexao.xml");
        Connection con = null;
        banco = (Banco) ctx.getBean("Banco");
        try {
            Class.forName(banco.getClassForName()); // Carrega o driver
            con = (Connection) DriverManager.getConnection(banco.getUrl(),
                    banco.getUsuario(), banco.getSenha()); // obtem a conexao
                                                            // com o banco
        } catch (Exception ex) {
            System.out.println(ex.getMessage());
        }

        return con;
    }

    public Statement getStatement() throws SQLException, ClassNotFoundException {
        return abrirConexao().createStatement();
    }

    public PreparedStatement getPreparedStatement(String sql)
            throws InterruptedException {

        PreparedStatement ps = null;
        try {
            ps = this.abrirConexao().prepareStatement(sql);
        } catch (Exception e) {
            System.out
                    .println("Erro com a conexao. Verifique se sua conexao esta ativa.");
        }
        return ps;
    }

我做错了什么？

Answer 1

据我所知，您的类(class)名称不同:

import model.Banco;

并且在 xml 配置中您有:

<bean id="banco" class="modelo.Banco">

您可以将 xml 文件更改为 model.Banco 来纠正此问题。

Ivan 已经评论过的另一点是区分大小写的名称。由于您正在请求名为 Banco 的 bean，因此您还需要将 bean id 更改为 Banco。

banco = (Banco) ctx.getBean("Banco"); // here your request it with upper B

声明是:

<bean id="banco" class="modelo.Banco">

尝试将您的 XML 更改为:

<bean id="Banco" class="modelo.Banco">