Problem Description:
A very simple spring project that uses static factory methods to configure bean instances. The directory structure of the project is as follows:
code show as below:
Car.java
1 package com.tt.spring.beans.factory;
2
3 public class Car {
4
5 private String brand;
6 private double price;
7
8 public String getBrand() {
9 return brand;
10 }
11 public void setBrand(String brand) {
12 this.brand = brand;
13 }
14 public double getPrice() {
15 return price;
16 }
17 public void setPrice(double price) {
18 this.price = price;
19 }
20
21 public Car(){
22 System.out.println("Car's Constructor...");
23 }
24
25
26
27 public Car(String brand, double price) {
28 super();
29 this.brand = brand;
30 this.price = price;
31 }
32
33 @Override
34 public String toString() {
35 return "Car [brand=" + brand + ", price=" + price + "]";
36 }
37
38
39 }
StaticCarFactory.java
1 package com.tt.spring.beans.factory;
2
3 import java.util.HashMap;
4 import java.util.Map;
5
6 /**
7 * Static factory method: you can directly call a static method of a certain class Return Bean instance
8 */
9 public class StaticCarFactory {
10
11
12 private static Map<String,Car> cars = new HashMap<String, Car> ();
13
14 static {
15 cars.put("Audi", new Car ("Audi",300000 ));
16 cars.put("Ford", new Car("Ford",40000 ));
17 }
18
19 // Static factory method
20 public static Car getCar(String name){
21 return cars.get(name);
22
23 }
24
25 }
beans-factory.xml
1 <?xml version="1.0" encoding="UTF-8"?>
2 <beans xmlns="http://www.springframework.org/schema/beans"
3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4 xmlns:context="http://www.springframework.org/schema/context"
5 xmlns:p="http://www.springframework.org/schema/p"
6 xmlns:util="http://www.springframework.org/schema/util"
7 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
8 http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
9 http://www.springframework.org/schema/util http: //www.springframework.org/schema/util/spring-util-4.0.xsd" >
10
11 <!-- Configure beans through static methods. Note that instead of configuring static factory method instances, but configuring bean instances -->
12 < bean id ="car1"
13 class ="com.tt.spring.beans.factory.StaticCarFactory"
14 factory-method ="getCar" >
15 < constructor-arg value ="Audi" ></constructor-arg>
16 </bean>
17
18
19 </beans>
Main.java:
1 package com.tt.spring.beans.factory;
2
3 import org.springframework.context.ApplicationContext;
4 import org.springframework.context.support.ClassPathXmlApplicationContext;
5
6 public class Main {
7
8 public static void main(String[] args){
9
10 ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-factory.xml");
11
12 Car car1 = (Car) ctx.getBean("car1");
13 System.out.println(car1);
14 }
15 }
Run the Main.java program, the console error is as follows:
Exception in thread “main” java.lang.Error: Unresolved compilation problem:
Type mismatch: cannot convert from Object to Car
at com.tt.spring.beans.factory.Main.main(Main.java:12)
Cause Analysis:
First, you need to install jre 1.5.0 and above.
Second,
set your installed jre in eclipse’s’Window”Preference”Java’ and’Install JREs’.
Third, in eclipse’s’Window”Preference ” Java ‘in,
‘ Compiler ‘was set up’ Compiler compliance level ‘of 5.0 or more
(the key is the third step, the compatibility level)
problem solved:
Since the jdk version I installed is 1.8.0, the problem should be the Compiler compliance level.
Go to Window->Preference->Java->Compiler and find Compiler compliance level=1.5
Change the Compiler compliance level to 1.8:
Run the Main.java code again, it runs normally, and the console displays the following information:
